Keep the action readable
The crop should preserve what the viewer needs: the player, target, objective, or decisive area of the HUD.
Plan for movement
Review the whole clip rather than only the first frame. Use framing changes when the important action moves.
Compose the facecam intentionally
When a reaction matters, place gameplay and facecam so neither blocks critical game information.
Review at phone size
Watch the finished 9:16 composition at a small size and confirm captions, action, and reactions remain legible.