hopefully someone can help

what do you guys think would be the best setup for a 150watt hps? like how many plants?

You could probably do 2 plants. A 250 watt HPS does a 2x2 area, now pretend each plant is in a five gallon bucket, each bucket is one square foot, that is 4 plants.

Wow that is a cool little formula I just made up. Does anyone agree ?

A square foot is probably what you'll need for each plant in a soil grow or DWC grow. Ebb and FLow or NFT you can probably get some different numbers.

how many would you recomment for a scrog?

I'm not a SCROG person you'll have to wait on someone else to answer or do some reading.

I'd say 2/3 SCrog.

You'd find it hard getting light to the lower branches, so you'd probably have to cut them off.

only 2-3 plants?

How many did you want to do ? Are you not going to believe us and try growing 16 plants under it anyway ?