Too much plant at m² ?

Shorten veg time, or top, or LST, or Scrog, or any combination of these. Monster crop the stalks that get out of hand. I've managed 12 5 gallon pots in a 5' x 5' tent and it was crowded, to say the least. A lot of time maintaining the plants to fit in a smaller space. I topped and defoliated much of the lower growth. The buds in the overcrowded grow were not the best I've grown. 5 5 gallon pots in a 5x5 gave plenty of space for the plants to fill in and they didn't have to compete much for light. On the other hand, if they are regular seeds, keep them all until the sex shows. So, you can be prepared to toss the males (if unwanted).