4x4 here with 600HPS, generally 600gram, touch more maybe 10% plant dependent.
5 plants in that space will give me no more than 4 plants in the same space.
4 plants in 20ltr pots is idea for 600+grams in my experience.
Sorry I don't have my grows to show as I'm new here but they are on RIU under the same user name as I use here.
Been growing decades and I have it very consistent with minimal effort.
Soil /coco, Ecothrive Charge and Buddhas Tree Organicus all in one feed and the proven trusty HPS. Nothing else.
I'm happy.