Did you try all your MX boards? The feel of the keycaps will largely depend on all the specifics of a keyboard's construction (plate, PCB, case, etc.). I wouldn't necessarily expect the feel to be same across all MX-based boards just because the switch is MX and the keycaps are SA.
My greatest issue with MX switches is the bottom out and upstroke noise they make. A silenced Topre switch is miles ahead of any MX switch (even their "silent" versions) in terms of smoothness and the sound they make. That trumps the specific feel of the tactility, though for me the feel of Topre's tactile bump is also miles ahead of MX brown, but that's absolutely a personal preference thing.
I dont really have any other boards or switches, just a few mx brown boards that are plate mounted with plastic cases.. Im with you on all of your points, I agree, Topre is the smoothest, sounds the best and the tactility is very different than the mx browns or probably even clears, but for some reason, the slightly gritty feel, the new sound profile that the sa caps give it and perhaps the near linear feel of the browns, I dont know, Ive tried to tell myself that it must be a fluke or something, but something about it just feels right, and sounds right and after typing with the sa caps for a while Im starting to wonder why I never tried it before and why I like it so much. There is a deeper tone to the browns now, which is obviously from the sa caps, but they also feel snappy for some reason, something I never would ascribe to the mx browns.. Maybe its all in my head or its just because its different from what I am used to, but Im gonna run with it for a while, i really do enjoy it, it just has this whole organic/mechanical vibe about it that I never knew existed..
My next board is probably going to be a abko hacker, I like being able to use mx caps with topre/clone switches, and that is one board that i have been really wanting to try, it comes silenced and has mx stems which I like, plus its fully programmable from what i hear.
I listened on youtube to some other people using sa caps on custom cherry boards and I notice they make a pleasant sound as well, at least to me.
Maybe I just need a week and ill get tired of it or something, but honestly the second I started typing on it I was shocked at how much I liked it, even typing now, I really like the way it feels and sounds.. Still to loud for an office setting or something like that but I work from home which isnt an issue for me. Topre has a mushiness about it that is borderline annoying, if it wasnt such a great board in every other respect I would just use my btc 5100c, which has better tactility than the realforce, granted Ive never tried 55g domes before, so I could be missing out on something there.
If anything Ill keep both going for a while to see which I end up using more. I almost want to grab one of the ramaworks kits and see if that makes the mx's feel even better, something with some mass to it perhaps.. All i have for cherry boards are ducky one, one rgb, and shine5, all with browns, they basically all sound the same to me.