I'm new the whole mech keyboard world. I have a keycool keyboard that I got from Massdrop and I notoriously bottom out. I read up a little bit on the o-rings, but I have no idea what size I would need/want to get. Any thoughts from the more experienced mechanical keyboarders out there? And to be more specific I have the Keycool RGB keboard with kailh brown switches.
whwar9739It's all a tradeoff, and everyone have their personal preference. With OEM profile, you likely don't want anything thicker than 2mm.
O-rings do make the keyboard quieter, but it also changes the feel significantly. Some people like the crisp bottoming out clack. Some people like the long travel distance of mechanical switches. But others like O-ring for making keyboards a little quieter, and also makes it less tiring when they do bottom out.
The thicker the keycap, the greater the reduction in travel, and the greater the cushioning. Since you're in the US, I'd say just get a pack each of the 1.5mm and 2.0mm as it doesn't cost you additional shipping. But if you only want to get one size, I'd suggest trying the 2.0mm