Out of curiosity, why yiffit in particular? Lot of nice people there for sure, but that can be said of most instances.
If you're going to only have a single account to keep track of, there are plenty of options that aren't as likely to be defederated, and you still have access to the yiffit content and users as well as ml content and users.
Mind you, there's more benefit to having multiple accounts than drawbacks, particularly for the nsfw stuff. I tend to block the majority of the communities that fall into the porn side of that on my main accounts just because I like my feed to be useful to me, and I have very limited use for porn/fetish material on a regular basis, but I don't bother on other accounts because it doesn't bother me to just scroll past on those occasional use accounts.