thats a cool little beginers indoor setup
now your thread title is kinda off seeing the obvious of two buckets in there and asking about yeild on two plants
but to stick to the title ,..smaller pots maybe four tall small ones
i started simular to your setup and grew eight small plants ..four on bottom four suspended on wire mess in the middle
but for that my lights were vertical (back and left right sides)

the only problem was shitty floro power useing no ballast and NO air vent as i see you dont have from the angles of the pics i can see at least ...assumeing your not gonna leave that open like that

but good luck and happy growing