The Macintosh IIci shares its RAM with the on board video, but you can also use a nubus video card for video as well.

Only bank A needs to be fully populated with 4 x SIMMS, you don't have to fill both banks, but they do need to be of the same capacity and speed.

Funnily enough I still have a bunch of 16Mb 30 pin SIMMS I pulled from a working Q950 and they work fine in the IIcx and II I have so they should work fine in the IIci as well. My IIci needs recapping so not working at the moment.