I had no idea there was even a Switch port in the works, super impressive they got it to run. Considering it was ported by the same team, I wonder if it looks anything like The Wither 3 did on the Switch. I was very impressed by that port, but it sure was blurry!
I played (still in the middle of KCD) both games on the Switch. Both do work good for what they are: ports who definitely punch above their weight!
I played KCD on the PS4 when it came out and I can tell that there are some compromises, like less details in the distance and choppy animations when a person is walking far away from me and framerate dips in crowded places.
Aside from some stuff like I mentioned above, the port is great and I was really surprised how well everything looks. If you want to play the absolute best looking version of the game you already have it for your pc anyway but if you ever want to have the most flexible version this is definitely a great port of a great game!