I've used browns, clears, ergo clears, Kailh Pro Purples, Jailhouse blues (two methods), Mathias, dampenned white Alps. Probably forgetting a few other tactiles.
I like a LOT of tactility.
Mathias are nice, but super fickle to get get right. My one board with them was getting dampened Alps as they're just better, but they just lack something, so it's on hold to decide what to do. Undampenned is too loud, dampened feel good, not great. They lack a snappiness I've come to like. If you do go Mathias, the one thing that seems common is that only Mathias can get them right. Something about how they are soldered.
I wasn't impressed with Ergo Clear or Clears, Clears were too stiff and I may have lubed the Egros wrong (it was a while back). I was unimpressed in the end.
The Kailh are what I'm currently using in the GMMK, I have softer springs arriving tomorrow. They ABSOLUTELY require lube and there are days I think they are fantastic (other than stiffness), and other days I think they are just horrible (and not a great sound, they sound muddy but feel crisp). I have yet to figure this out, hopefully the springs help figure it out.
My current favorite though I do not have a board full of them and that can lie, is 62g Zeal Zilent v2s, I'm just waiting for the fire in my wallet to stop burning before I make the purchase. The testing with them I have done though, I like. I also have some regular Zealio v2s coming this week to try. If they were cheaper, I'd be all over them. Great right out of the box.
Side note, if you don't mind some click, Box Jades are another good choice, but they feel stiffer than they claim (I may just be over sensitive after using the Filco for so long (sub 40g activation). Nice sound, not extreme, at least for me, and great feel, except for how stiff they are. I'm waiting for springs for them before I make a final judgment. I really want to like these, as they are very similar to wired Jailhouse Blues.
What I recommend doing is getting a switch tester.
That can be a spare plate, something purposely made, or a hot swap keyboard. Then buy sample packs of switches. It's still not cheap, but cheaper than a mistake. I have a bunch of others but these are the primary ones.
I agree with Riverman, stabs can make or break a board, once you have had decent ones, it's hard to go back to anything less. For Cherry style look up "band aid mod" and for Costar, just coat everything in Super Lube Dielectric grease.