2 would be better, but you could still face overcrowding if you let them veg too long.
Also depends on the strains you're going to grow... Sativas will want to grow taller, while Indicas will tend to stay shorter & bushier.

LST can work wonders... If you're gonna do it, start early (at around 2 weeks) to promote some bushiness, then switch to 12/12. Remember, most plants will double to triple in height once flowering commences, so use that as your guideline as to how long to veg.

Autoflowering Lowriders are a strain that stays really short, and flowers automatically, no matter what light photoperiod they're under. They're fast-maturing and will show sex in 2-3 weeks or so. Good choice for height-challenged grow spaces