I hope Apple implements it how they already do with the Back Tap accessibility option. By giving a preset number of system / accessibility features, and then listing the user’s shortcuts library. Otherwise, it would be weirdly restrictive of them.

Not OP, but I wouldn’t say there’s any major differences. I did notice they were slightly stiffer when I first installed them, though after a week or so they feel totally smooth. Precision feels the same, definitely not worse.