I see. What does that change in terms of process needed?

BGA you need hot air and reflow but a QFN I think you can just position and solder by the side with a simple solder iron with a knife like tip.

BGAs generally call for more complicated reflow profiles (including vapor phase reflow for very large BGAs - think 40mm+ FPGAs) and require X-ray inspection (if doing inspection at all.) BGA balls can have under-body solder voids, etc. BGA devices also generally specify a specific solder to use (leaded or lead-free won't be interchangeable.)

Generally, all single-row package pin layouts are easier than double-row (BGA, WLCSP, 2-row QFN) to reflow.