what height to flower at, should i fim or top?

i have 9 cheese plants, almost 2 weeks old, in a 1.2m x 1.2m x 2m (4feet by 4 feet by 6 feet) grow tent under a 600W hps, i am wondering wether i should top/fim them when they have the required amount of nodes or train them in other ways. Would there be enough space in my grow room for my plants to grow bushy or should i keep them relatively small to prevent them from competing for light in the amount of space i have? i am planning to transplant them into 5 gallon pots when they are ready (don't have other sizes), would this work?
Sorry for all the questions in one, I would greatly appreciate any tips and tricks anyone might have! I'm very concerned about taking care of my girls as well as i can for my first time!

That's a lot of plants in a 4x4 space. Not sure you want to FIM or top these at all. Might be better and a faster veg time to leave them as a single cola each. I would aim to keep them short and bushy but more than even just a few colas each might get too tight in there.
If heavy yields are your aim the best option might be to top them, let them veg out and then weave the colas into a scrog net. You can make a training net out of some cheapass twine or dolla-store clothesline. Tie a length of twine to all 4 corner poles of your tent and then tie some even lengths vertically and then horizontally to form like a grid; tie them loosely and loop each crossmember so they can easily slide & adjust to support your plants as needed. Only trouble is with a scrog net inside a tent makes it a real pain to water them. Be creative; I used to water plants with a PVC pipe to reach the plants in back.
A good rule of thumb is to top or FIM when the plant reaches the fifth node: plants from seed start out with baby leaves; don't count those. Then the first set of true leaves is the first node. Let the plant grow out 4 more sets of lateral branches until the fifth set of nodes emerges. Wait til the leaves begin to pray like tiny hands and snip completely off to top them or leave a knub to FIM.
Flip your plants to bloom phase when they are 2/3 as tall as you want them to finish. They will typically grow another 30% larger during flowering. Transplant to the 5 gal pots when your plants a few days or so before you want to flip them so that the fresh soil will feed them through most of flowering.

Thank you very much for putting in the time and effort to reply so fast, I appreciate it greatly! I will definitely follow your advice on not topping or FIMming these plants to avoid any complications since i don't have the experience to maintain optimal conditions yet! How tall should i let them become before flipping them, considering that the 9 plants get light from 1 lamp in the 4 by 4? I want to prevent flipping them too early or late to maximize the plant's potential! I do plan on topping/fimming and scrogging my next grow, how many plants would you advise me to start off with in the tent I use? Again, many thanks for your answers! You've really saved me here because I had no clue what would be the best options for me and was scared I'd mess up the plants! Now I've got a view that's a lot more clear on how to continue growing!