How many plants to fit in my new tent?

Hi I'm thinking of doing a grow with subcools super soil in 20ltr airpots in a 3 x 1.5 x 2m tent using 2 1000w lights with 6" cool tubes. I was wondering how many plants I should do without overcrowding? and if I veg for 2 weeks in 6ltr pots then transplant into the 20ltr airpots half full with super soil how long should I carry on vegging to get a nice root mass before budding? I'm thinking of doing big bang as they're meant to be 9 weeks but my friend has lemon haze and cheese cuttings so not sure which to go for any input or advice would be much appreciated. Also should I ph my water with super soil? I'm using bubbled tap water which is normally 7.6-7.8.

Yeh it's 4.4 gallons and 10x5 I was thinking an 8" fan and filter for the heat but summer is approaching here in the uk and hope it'll be enough to keep temp down..

I might get a smaller 4-5" fan to suck in cool air from the window but I'd prefer the tent to be sucked in a bit so I know all of the smell Will be sucked thru the filter..

There is a most famous post on ventilation here well worth a read, and have used the math myself with glee and much token done by all
..https://www.icmag.com/ic/showthread.php?t=112862

Epic info in the link vostok.
Most informative.