For [0], libinput from what I've seen is supposed to take the place of linux-wacom. However I have only been playing with wacom fairly recently (I got one as a Christmas present) and haven't explored linux-wacom to see what is missing. I know with respect to libinput I have had difficulties getting the extra buttons on my tablet to work and some things have been a bit rough, but I don't know if that is due to me not understanding something or what.

TL;DR Theoretically libinput is a linux-wacom replacement.