the gavitas run kinda seem like they actually run a bit cooler than a bare bulb 1kw hps judging from a homies room, 2 ton for 4k is plenty from what I've been lookin at(I found a 20 or 30 SEER 2ton mini that only pulls 6amps @ 240v...basically only 1500w consumption for a 2 ton, I believe it was an Lg) I believe it's light intensity that causes the issues more than heat necessarily
FWIW...a sealed room is much easier to control odor wise...
Use darkroom louvers to provide some passive exchange between veg and flower...
You BLOW into your filter in a sealed room as opposed to pulling through it. Get a BIG filter (150) and a 10" fan and you'll be fine. I'm pretty sure Phillthy was using the same filter for pushing 3 years and still not any smell at all.
Think about it - if ZERO outside air is being exchanged - your chance of having smell escaping is technically LESS than if you were pushing air out and pulling in more...
As long as your minisplit (probably go with minimum 3ton for 4k) is adequate to cool the room - you're set.
dank.Frank