@OP: Maintain a single direction for airflow ie from lower front intake to upper rear exhaust.
NZXT Source has 2 front intakes. One for HDDs and the other to feed the CPU cooler.
Optional:
Bottom intake can push in a lot of dust from underneath the cabinet. Opt for this if you can keep the cabinet base clean.
Top exhaust are ok and prevent dust filtering into the cabinet from the top vents.
Personally, I avoid side intakes since they intersect the defined airflow and dump a lot of dust on the GPU(s).
Side exhaust might be needed incase of multi GPU configs.