A lot of just "1 episode" appearances from old characters

IMDB is not reliable for this sort of stuff, that's entirely arbitrary. James, for one, is gonna be a major character.

They put "1 episode" for anybody (in any series) where they don't know the exact episode count (and how could they since nobody has watched the series?). In reality, though, it's probably not far off. Probably many cast members, whether they're original or new, will only have one or two scenes, let alone one episode appearance. The cast is so large. Does anybody expect Gary Hershberger to appear in more than one scene?

I think a lot of the cast will appear in like big gathering or party scenes. Lynch sometimes has well-known actors appear in very small walk-on roles, like the credits scene of "Inland Empire". They can't possibly all have significant screen time.

I was surprised by this too, glad to hear an explanation that makes sense. The most shocking was Sherilyn Fenn, I was expecting her to be in a lot of episodes. Maybe she will be *fingers crossed*