Data center fiber between racks.

So been wondering about how smaller datacenters (10000sqft) run networking in a rack, between racks and between rows? Are unterminated fibers run and terminated for everything? Rack only are using patch fiber or mix of patch fiber/ethernet? Better to have TOR of EOR switches? Would be probably mix of colo and on premise servers? Wondering cause possibly getting into setting up some datacenters and I know there's a million ways one could do it depending on tier and funding.