my advice is to get a base keyboard first, then make your way to understanding characteristics of different keycap material, hence a decision. If you need LED, options are shrunk down significantly

Actually, you don't need much guide for led modding on poker2, it has the slot and circuit needed for led backlit by default, all you need to do is to solder off existing solder on the holes, plug in your led and resolder it.

For more details, pay a visit to the mechanical keyboard thread in hardware section, some poker2 owners there that had done the mod sure willing to assist and guide you.