you could also run 6 cobs on those 2 drivers and add 2 cobs later if you wish
you have reflector adapters but no actual reflectors. not sure you knew that. i suppose if you wer eplanning on adding reflectors later you could put the adapters on now just to be ready so youre not climbing up over your girls with tiny screws and screwdrivers to mount the adapters later. clicking on reflectors is a 5 second one-hand job
heatsinks come with screws, id order (4) 2-slot wagos for easy wiring, im out of wire right now, you could pick up 18 ga solid wire locally (home depot t-stat wire is popular)