Co2 is awesome dude,
but for LEDs... dude 1200w is real but light loose its power in further distance, tops of your plants in good distance from your LED reaching enough light, but as it gets ...further there's not enough power in it,
I've read before that 6000 lumens per m2 is essential for growing but this lumens is produced only in 1 spot, if it's get further it's not good anymore .
there's same output in 1000w hps and 1000w LED, the difference is in electricity used.
and the structure of light, hps and mh are scattered, but LEDs are straight.
you can get 6000-8000 lumens with both,.... but one in 30cm and another in 60cm high up the plant for example,
you know light is something that plant can get it as long and as much as sun would bring! so in my opinion much is better!
by rising your co2 levels and nutrients level you can put your light even closer, don't forget air circulation,
bring your light toward your plant don't be scared , give them a little light stress and judge your distance by that.