How exhaustive should I be when enumerating works in a State of the Art
It is difficult to give a general answer to "how much detail do you need to summarize", since that depends on a lot of things, but you should first of all ask your supervisor what they expect. That is always the definitive answer to "how much is enough" regarding a thesis: it doesn't really matter what answers you might get at Academia SE; what really matters is what your supervisor (and thesis committee) accept.

That said, if your goal is to provide the most useful information for researchers that might read your thesis, then I would suggest that you be as exhaustive and detailed as possible. If you have gone through the trouble to read these articles (at least enough to actually understand the differences between various Muffin equations), then it would be very helpful to others for you to spare them the read by summarizing what you have read and understood.

From what you describe, though, I don't think writing a textual paragraph would be the most helpful way to describe this information for your readers (nor the easiest for you). I recommend that you present these details in a table which cuts out all the fluffy words and just gets to the point: the name of each variation; the citation of the article that presents it; the key details that distinguishes it from other variations; the pros and cons. In addition, if you could group the 20 variations into three to six categories that are similar to each other, that would be a further helpful layer of synthesis.

There are two further advantages of using a table:


For yourself, a table helps you focus on what is essential in each article. By carefully thinking about the structure of the table (mainly, which columns are necessary), you help yourself to better understand what you're reading and to focus on what you consider important.
You don't need to worry about which ones are "worth" summarizing or in how much detail: you just simply summarize everything, briefly and to the point. That said, if a few variations stand out to you as important, then by all means write as many paragraphs as you want to that discuss these ones in detail. But then you won't need to do that for any of the others that you have already briefly summarized.