what controller you using? .... wireless, right.
sorry, was still thinking promicro... 5v
nice nano is 3.3v on board. lipo would range 4.2-3.5v-ish (depending on what power circuitry is on the nice nano)
sounds crazy for as little as you want to do (5 keys), but you'd probably need a step up 5v regulator that. the step up part is important because your input voltage will be less than your output. (some regulators only step down). you could probably do it with a simple mosfet as well, just make sure you get the type of fet & the calculations correct.
as for caps...
- translucent, blank. - these are clear or transparent colored caps
- shine through caps - prettymuch only the letter or number should shine though
- pudding caps - similar to shine through, but have the lower half to 3/4 a white-ish plastic that the light will shine through
the latter two will probably only be available in full sets unless you can find just a 10-key set for a numberpad
use these terms to do some google searching and you'll see what i mean.
footprint...
https://github.com/keebio/Keebio-Parts.pretty/blob/master/SK6812-MINI-E.kicad_mod... of course keeb.io would share the footprint (love these people)
should be able to find in Ki-Cad smd led library
https://kicad.github.io/footprints/LED_SMD