Do non religious Universities care about grades in religious classes? For example I have a Bible class - if I were to get a B-, would universities even look at that?
Yes, of course they would look at those grades - they’re classes you took! Many religious classes rely heavily on reading comprehension and critical thinking - if you do not do well, that may very well look poorly on any college application.
It depends upon the college. But if an AO is viewing a transcript from a Catholic HS, for example,s/he knows that the HS requires a religion course each year and that the HS treats it as a core academic class. So if your question is “Can I blow off my religion class?” No. If your question is "Will a B- in religion (or any course) be an auto rejection? Also no.
It also will be part of your HS GPA.
I heard one AO of a top tier non-sectarian college say that they view Philosophy/Theology as academic coursework similar to a SS class. I’m sure there is variation from college to college though. That said, one B- in any academic class won’t lead to an automatic rejection from any college.