You should inspect a Cherry MX switch; you should be able to see precisely what parts of the plate contact what parts of the switch housing. There aren’t too many hard requirements when cutting plate holes, but I’d recommend:
(1) try to get at least one part of the plate reasonably tight against each side of the switch. You could probably hold the switch from just two opposite corners, or along the sides somewhere, but a tight hold at all 4 corners is the popular approach.
(2) try to get the little plastic clips to securely snap into place
(3) (optional) leave space for the top housing to be removed without needing to desolder the full switch (personally I think this is an unnecessary gimmick, but many folks seem to like that feature)
Other than that, do whatever you want, go nuts, experiment.
I have been looking closely at the switch to understand the choices for some of the cutouts. That's why I got confused by #4 (the one with insets on each side and cutouts at each corner to allow rotation). We need a name for them. Or acronyms. R - Rotatable, C - Cutouts for modding, I - Insets for stability
1: R
2: C
3: CI
4: RCI
So the RCI cutout confused me, because I didn't understand the need for all those cutouts. Reading that thread really helped though.
I was having the most trouble with trying to get everything to fit tightly and have the tabs snap. I created the hole with a dremel and a routing bit, and then hand filed the rest down. I tried creating the cutouts for modding, but I don't see how you are even supposed to use them while the switch is mounted. I've successfully opened a switch not mounted, but I had to pry the tabs up. I also watched Litster's video but that also didn't make any sense.
I'm most likely going to choose #2/C because I think I'd like to be able to try out modding at a later date and I want it to be as easy as possible, even though I don't know how to do it yet.
I think this is the same topic, but how do stabilizer cutouts work? I've seen several different designs, from the ones on the ergodox plate to the infinity keyboard on massdrop and they look different in several ways. I know there are plate mounted stabilizers and pcb mounted stabilizers, but I can't find any resources on how they work.