I have a 600w 4x4 on my first grow right now. A couple plants that have been vegging for a couple months now in 5 gal pots look like they will fit perfect in there, of course factoring in that they will double or triple in size once in flower.
Anything much more than 4, I'd think you're overcrowding.
400w is weak for a 4x4. I would only do one and LST till she is a giant bush then flip her. Also I would not do any low yielding strains. Right now I'm doing 16 5gallon grow bags in my 4x4x7 under a 1000w. Im doing 16 single cola Ghost Train Haze #1.
All depends on what you wanna do.. I'd do a 60 day veg on one plant.. top it.. throw her into flower and scrog it.. I grow 4 plants under a 1000 watt hps in a 4x4 light foot print.. It just all depends on what your wanting to do
well I have 1 plant goin in it and don't see room for others but I top my plants a lot so was thinking next grow I wasn't gonna Top them to make more room ..will it make more room? thanks here's the plant in it now it's godbud