for 1. The cons? A super restrictive platform (even more than it was under intel) You can still boot arbitrary unsigned OSes - Apple still allows this, but it is obviously going to take time for other OSes to grow support for apple's custom hardware. So it's still a computer you can control if you want.

for 2., wayland is still a very rough experience imo (I periodically try it on an all-intel system, which ought to be a good target as everything is OSS supported, etc). Lot of apps still don't have native wayland backends (although this is improving!) and it seems generally less stable than boring old X11 for me.