This is particularly likely if your book is to be part of a publisher's series, and you and they want to maintain a consistent look-and-feel throughout the series. So some choices, such as type and basic layout, may already be made for you. This is even more likely to be offered for cover designs with a book series.
Templated designs are also what you will most likely encounter when working with a POD publisher. You probably will have an option to do your own original design, if you choose, but a range of templates will most likely be where you start.
There's nothing wrong with templated design, or using an existing template if it appeals to you. But it's best to avoid just using the template as offered. At the very least, you should personalize your book cover, modify the template, make it look enough different that it looks like something new and original. After all, you are publishing your new and original writings, so having a book cover that looks like a million others rather defeats that purpose.
Series titles do need to look similar enough to each other to be recognized as a series. But what carries the look-and-feel across the series may be the master logo, the titling font, cover art placement and size, and the series title, especially if the series title includes a logo design. Other than that, the cover photo and background color, and some other elements, can be quite different. The series is linked by some key elements staying the same from cover to cover, while others vary.
Within any templated design, expect to be given only a range of choices. For a series, that's no problem. But if you want your book to stand out from the crowd, to be more attractive to and noticed by the reader, you might do well to think outside the proffered box, and either design something that is not based on a template, or hire a designer or design consultant such as myself to help you make those decisions. Really, the most important element of a template is paper size: what is your book's actually printed size going to be? With modern printing technologies, POD or otherwise, that's a blank slate that can be filled many different ways. So don't just settle for what's provided you, do something with it, make it yours. (Of course, as I've discussed before, there are writers for whom the primacy of the word is so powerful that it blinds them to all other aspects of the reading experience, including design. In which case, if all you want is a handheld container for your words, use the template as is. Just don't expect to get noticed by many readers.)
The big publishing houses to whom a writer just hands a manuscript and has no say in the design, the big publishers who maintain their own in-house design staffs and marketing teams—those publishers still exist, but their in-house one-stop paradigm is no longer the dominant paradigm, and is now only one of a wide range of options.
As a writer who is self-publishing, you will have to make at least some design decisions. Get used to it, as it's unavoidable. The more design decisions you keep you hand in, the more of a feeling of controlling your own destiny you will have. Some will dive in and view that as a creative challenge. For others design choices are too terrifying to contemplate; but you must. Yes, all this is a distraction from the actual writing: but every business-level decisions regarding your book that you must make is in the service of the writing, and is intended to support your wallet, so that you can get back to the writing as soon as possible. As a writer who is self-publishing, you must consider yourself to be a cottage industry. You can go so far as to make t-shirts to promote your book; online POD printing is not limited to books, but can include everything from fabric printing to coffee mugs to CDs. It's all available to you. Your only limits as those within your own imagination. (Okay, and stamina. This can take a lot of work to get it all done.)
Since no one else is going to take charge for you, I encourage you do yourself a favor and take charge for yourself. You might be forced to do this anyway, so I encourage you to embrace it as a writer, and do it. Use it an opportunity to learn some new skills and ideas, and as an opportunity for self-empowerment. Treat it as a positive experience, and good luck.
It's a big pond with many fish in it, and some of those fish will insist on viewing you competitively. That can't be avoided, but it also doesn't have to be confronted. Personally, I like big ponds, because I'm not an inherently competitive person; I've always felt that the pond is big enough for all of us, in all our infinite diversity. On the other hand, I'm not a doormat, and don't let people walk all over me. The point here is that you can make your own corner of the publishing world, be happy and do well, and not worry about the other guys.
On the inside of the book, most publishers will offer only a limited range of typefaces for body copy, usually choosing a "house font" that they prefer most body copy to be set in. This can be a matter of taste. You may be asked to make these decisions; with templated design, you more than likely will.
Different publishers will choose different house fonts, to the point where an experienced designer can pick up a book by a certain publisher and know which typographic specifications are probably going to be used. This is part of how a publisher establishes an identity, the look-and-feel across all the books within a specific imprint.
One approach in typography emphasizes transparency, in which the design and type choices are meant to serve and clarify the text. There are other movements with typography theory, but this basic principle of readability is the one you are most likely to encounter with publishers who use templated design. This approach is exemplified by Beatrice Warde in her famous essay on typography The Crystal Goblet:
Imagine that you have before you a flagon of wine. You may choose your own favourite vintage for this imaginary demonstration, so that it be a deep shimmering crimson in colour. You have two goblets before you. One is of solid gold, wrought in the most exquisite patterns. The other is of crystal-clear glass, thin as a bubble, and as transparent. Pour and drink; and according to your choice of goblet, I shall know whether or not you are a connoisseur of wine. For if you have no feelings about wine one way or the other, you will want the sensation of drinking the stuff out of a vessel that may have cost thousands of pounds; but if you are a member of that vanishing tribe, the amateurs of fine vintages, you will choose the crystal, because everything about it is calculated to reveal rather than hide the beautiful thing which it was meant to contain.
The basic idea here is that design needs to be "transparent" to content, and not draw attention to itself. The caveat is that bland design draws attention to itself as badly as does gaudy design. The proper vessel for the content is something balanced and appropriate. It can also be elegant and clear without drawing attention to itself, and away from the text.
If, for example, your book is a prose text about history or a murder mystery, one of the classic serif typefaces such as Palatino, Weiss, or Garamond will make your words look classic, orderly, and somewhat elegant. If your book is a how-to manual for computing, an elegant sans-serif font such as Optima might be a better choice, especially if your text is heavily illustrated with examples and samples. The famous serif monospace typewriter emulation font Courier looks just like a 1960s typewritten document, which is ugly for any usage but that one. Helvetica is a great typeface that is overused, misunderstood, and often poorly applied, so I'd recommend avoiding Helvetica except when you really know what you're doing and want that sleek clean Modernist look.
Another significant pole of typographic design is the opposite of what Beatrice Warde advises: when the text becomes its own illustration by pushing past the pure words on the page towards decorative, even "illegible" design. The schools of punk and/or grunge typography are examples; a lot of CD cover designs use "illegible" fonts as art-elements to set a tone of punk attitude, for example. David Carson's innovative design for music and skateboarding magazines such as Ray Gun exemplify this approach. It completely turns Warde's principles of 'invisible design" on their heads. Design like this draws attention to itself, and becomes itself part of the reading experience.
I like both these poles of design. I use what's appropriate for either. I use what I think enhances or illuminates the text, that amplifies the mood or tone or idea in the words. I set no limits on taste or what is acceptable in design, because in every case it's still in the service of the text, of the reading experience.
My idea of typographic "transparency" is therefore that the type should be treated just as illustrations are treated: in ways that enhance the meaning and tone of the text, and augment the experience for the reader. A punk type on a cover design about drug culture, skaters, and rebellious teenagers would be entirely appropriate; the same typeface would be entirely inappropriate for the cover of a jane Austen or Charles Dickens novel. Kerouac, maybe. William S. Burroughs, definitely. Herman Melville, not so much. Use your personal taste, make appropriate choices, and this will carry you a long way towards giving a good experience to your readers.
Once again, when you POD publish, or self-publish through other sorts of online media, the bottom line is that visual appeal of your book, the fact of its appearance will serve you well. You might have to spend some time figuring out what you really want. You might spend some time playing with the provided templates, till you achieve a good look for your book. It will be time well spent, and your readers will thank you for providing them with a more sensual reading experience than merely blank words on a dull page.
Never underestimate the power of the non-textual aspects of publishing. They can make or break a reading experience.
Don't just use what is given you in the templated design box. Think outside that box. See what you can do, given what options you have. You might have more flexibility than at first you conceived. All of this will serve you in the long run, even if it seems overwhelming at first, and improve your book's chances of being loved by giving your readers as pleasurable an experience as possible.