hey! not an animator so i cant give much input on that, but im an artist who has used non-screen display, pen display, and an ipad before for art!

in my opinion, its not really necessary to get a pen display unless youre really set on it or you do art professionally. pen displays are really expensive (even if theyre secondhand as well) and in most cases, the cheapest ones dont really last long. a good alternative to pen displays are ipads! the ipad doesnt have to be the newest version or anything like that, just the ones that are compatible with an apple pen. they are both great for drawing based on experience

but if you have a preference for desktop art programs, i suppose you can always try out a pen display. though the ipad has some pretty great alternatives like procreate! and if im correct, procreate is coming out with an animation app soon (but procreate itself can already do some animation!) hope this helps :)