Vegg to about a foot and a half and most strains will double in flower.

If you want a SOG then each stage will need it's own system for that stage. Such as drip or bubblers are easy to keep separate.

4 x 8 you got room for many. I would go 10 gallon tubs with 4 to 6 plants each and you could easy put 6 to 10 of tubs in there.