Hey darbolah, looks like your well on your way to a good setup. I'd say for a first grow you should be happy with anything over 2 oz per plant. It's gonna depend on a lot of stuff tho, what strain ur growing and all the variables like length of veg and the grow conditions etc. I'll try to answer your questions as best i can.
Should I add more plants?
Get as many in there as you can lol Just allow for how big they'll be when fully grown.
How long should i veg?
This depends on if ur growing from seed or clone, from seed try and give them 2 months veg to allow for full maturity before switching to flowering, this will probably require some topping and/or lst to keep them short enough so they don't get too tall when you flower. If they're clones they won't need as much time to reach maturity, you can probably put them into flower somewhere between 3-4 weeks.
Should i sog, scrog or lst?
Again this depends on the strain, some plants are better for sog than others, personally i'd have a bit of an experiment with whichever one you wanna try or mix them up and at the end you'll know which one works best for you.

As far as the temps go, i'd be a little worried about them. Plan ahead, is it likely where you live that the temps are gonna get higher? If so you need to sort them now rather than have them get any higher and it start affecting your grow. Like Grey1223 said co2 will help the plants tolerate the heat better but it can be kinda expensive. When are your lights on? If you don't have them off at the hottest time of day you should do, it'll be easier when you flower obviously as the off time will be longer. I have my lights on in flowering from about 10pm till 10am.

Hope this helps