If you planned on a bigger tent in the future id definitely get the 185-700 driver. Use the cobs you have and keep it as simple as possible. Sure you could add and change things up now but it's not worth the hassle for the small gain.
Yes I have a 3x3 with a hps 150 in there atm Just can't use it no more till I move need space so I went down some closet to small and heats a factor.
So Yes I want max efficiency and great yield its personal for me and wifey trying also to start a perpetual would need help on that on another time.
So yeah 2 tents 2x2x4 best efficiency and best yield would be c700 or c1400