Need some guidance with plants!

These girls are about 5 weeks from seed now.. been trying to use LST on them. Question is how tall will the get after I switch to 12 12 because I’m limited on my space and I’m most likely gonna have to just use these t5s to flower with so was going to ScrOG and keep them short?! Is there some critical things that I need to know just don’t want to fail completely! Thought and knowledge please first time grow for me

The plants can double to triple in height during stretch. Also, I don't think the T5s will do very well for flower.

Ok I own a 1000hps but just worried about temps of the room I’m in now... even with exhaust I think I will still have temps over 80 degrees.. I don’t want to run an ac because it’s just for personal anyhow don’t want to get super deep into pockets...