It really depends on your preference. Right now they would produce around .5-2 ozs a plant depending on your strain and light, but the longer you veg the more they'll produce.
Guess efficiency is what I'm going for - ideally they would be slightly overlapped but not crowed to the point they were outgrowing the table / light.
I would wait, way to small. Wait for mor branching and growth. I would top them all right now to allow the shorter branches to grow taller.