GMMK 3 Pro RGB & case question

Since you are going from a Corsair, I would recommend the Glorious Fox switches or Gateron G Pro 3.0 Sliver Switches as linear switches are typically better for gaming. AKKO makes some great budget Silver switches too.

If you like the feel of tactile switches, those are “okay and safe” for a budget. People would need to know your budget on switches for other recommendations but for maximum RGB, make sure you are looking at clear switches, North facing PCB and some type of shine through keycaps. South facing PCB will impact most shine through keycaps as the legend is more toward the north than south so the shine through isn’t as good. Just some other things to consider when looking at RGB compatibility.