Stick to 24/7 air movement, this will prevent air from getting stale and will prevent air from stratifying (developing uneven layers of heat.)

If you're thinking of doubling up on 90s in the flowering cabinet, I'd suggest you find a good 50w LED to drop in the veg chamber. I know mine is too much for two plants, maybe three or four would have been better but I didn't have a box with enough room.