Whats most critical. In your mind?
Achieving critical mass. It is really hard to hear 2 or 4 panels alone having a big difference in a room unless it’s truly very small. Consider at a minimum 6 units. Two corner bass traps and at least 4 more panels.
I would say the front of the listener, in a hemi-sphere, is what’s most important (unless your seating position is right up against a wall).
The floor and ceiling between listener and speaker are among the reflection points to consider. The floor between and behind the speakers. The corners.