first time grow. few questions on setup. temp and humidity

Hi Guys, Just wondering if you can help me out with a few things.

I have just built a sealed room inside my shed which is 2.7meters long by 2.5w x 2.5h and is lined with white plastic. I have a scrog bed on each side and will be growing 4 plants. I have 4 shades and will be using hps for grow and veg, what wattage would be best suited?
I have two 300mm bathroom style fans mount in the walls at foot level for intake and an rs200 for exhaust with filter and silencer. I also have a couple of destk type fans for the canopy

My main question is how to control the fans and humidity. where i live (New Zealand) is low humidity all year and lowish temps most of the year except summer. I have come accross a way to modify a cap air 2 to control a humidifier and temp instead of a dehumidifier and temp.


So how should I have my fans set up? does intake and exhaust need to be on 24/7 or just when the lights are on? does there need to be airflow when the lights are off? should they run off a timer so they come on when the lights come on or should they run off the cap air2 so they only come on when the temps come up? ifso should the canopy fans be the same or set up different?

Sorry if these seem like stupid questions but I have searched and cant realy find anything that answers them. Cheers guys.