2 5V/16MHz Pro Micros with pins (official, blue clone, or black clone), pairs are also available at RGBKB. The PM will have limited brighness compared to the Elite-C. Also compatible with the Elite-C and Proton C. Proton-C does not have working split code yet.
The Type-C ports are difficult to solder. Screwing them up can result in damage to your controller. Only proceed if you can test the board after soldering and make sure there are no shorts.
MX switches which support SMD LEDs will give the best backlighting effect. Almost all Kailh switches have a cutout for the LED. Kailh BOX/Choc switches will not be able to have their tops opened after soldering. Any switch with a transparent bottom housing will work great.