given your height limitations you won't get any benefit from the larger pots anyway. go small and lots of plants
You should use way smaller pots than even the smallest ones you mention. A sea of green with 16oz to 1 litre containers packed in there, that way you don't have to do anything like training or topping and you just let them grow into a sea of single cola's naturally. It will be the largest yielding and fastest way to grow in a space like that.
even with topping and training your space is going to be tight. 18 inches for the light plus 10 inches for the pot leaves you 32 inches for the plant. given that small size and that training is an extra step, you're probably better off with more plants of a shorter strain. the other approach is to shorten or eliminate veg and produce a lot of small plants in a short amount of time.
Great info OregonMeds. Just keep in mind the sea of green is meant to be done with clones so all the plants are female and grow and mature at the exact same rate.