peace guys

i have a lil problem with transplanting. i decreased my grow room size,and i have left 15''x15'' space for pots. i have 2 mother[i think

] plants,they arent so big,so i dont need to worry about height
what do u suggest,guys? i have very small horizontaly space. and i dont know what kind of pots to use. circular or square type? im worrying because today i saw some roots in bottom. so-its time for transplanting.
p.s - im making 2 in 1[vegging and flowering room,for some plants. because yesterday i got some new seeds,so i will put them in smallest 'room' and also yesterday started flowering in this [15''x15''] room