My first grow was at same size closet and i had two plants in there. It was my first grow so nothing really went like it was supposed to but In end of the day i made my money back 7x so cant complain.
I had some kinda sativa strain and light was too far away so plants streched out too much. I think if u have like some indica strain and dont let plants grow too high, u can certainly do it. But i suggest u to get 4x4 tent or something for future.
If i was doing grow on that sized closet again, i would propably go with SCROG netting and i think u could fit 3 plants In there. It would shorten the time on veg to get whole area covered.
I am doing 5 plants in a 36"x30" just veg till space is filled then flower, whether its 1 or 4... The less plants the longer it takes to fill canopy, thats all..