I use dampeners with MX Blue, so that I only get the click and not the clack (sound from bottoming out). The Red O-rings are the smallest from WASD giving the smallest difference in feel.
I have tried O-rings on MX Clear and MX Brown also - they are unnecessary on Clears and I feel that they dampen too much on Browns.
Laffindude said it. The Caps Lock and the Space Bar have different switch positions on the G80-3000 than on WASD Keyboard's own keyboards. The other keys are compatible.
Note that WASD's keycaps also have a higher profile than Cherry's caps, the so called "OEM profile" so that using mixed keycaps can be weird.
Custom key sets in Signature Plastics' DCS profile are often more compatible with the G80-3000, even having practically the same height, but AFAIK they are incompatible with O-rings.
Cherry's keycaps are usually of pretty high quality anyway, being made of thin PBT or thick POM plastic ... or in the case of vintage keyboards: double-shot ABS plastic, which is in high regard.
Another option, if you have grey Cherry PBT keycaps may be to dye them in RIT-brand fabric dye. It is not that easy to get a perfect result, though, but many have done it and there are threads about it on the forum.