I was waiting for someone to say something. Im no indoor expert but (have some friends that are) I do know everything you say is on the money, Also, if I was to just say one thing, doesnt 12 plants seem like a lot for a 7x7x8? You did the right thing coming here Pauly, guys like mr4 can save you a lot of headaches, disasters, and money that one can only avoid with experience. Always good to see somebody passionate about growing. And also see somebody step up and let another know when something is a little off. Kudos Mr4
Holy shit I didn't even see he said 7x7 lmfao. Yeah thats alot of light for x4 1k's omg. Good call pointing that out dude.
Access, humidity, and coverage are factors that seem to get overlooked...
A single 1k over a 4x4 is pretty intense how it is. Most guys in multi-light setups with 1k's are using a 5x5 footprint.. Your also going to have lighting overlap from using multiple lights so the intensity will be even greater... Now that I see the room measurements, your footprint per light is 3.5x3.5 which is overkill by quite a bit even if using only one light. I honestly think your better to go with 600w's, or run x2 1k's and leave yourself aisles on either side of the room. With 1k's in that little amount of space your margins for error and environment control are minimal. It's going to be quite the juggling act.
To explain it, consider available space... Your ceiling height is 8'. If your lights are maxed out at the ceiling, your going to have the distance from light to canopy (which depending on who you ask / and your venting temps thru lights) can be anywhere from 12" - 30". So lets say even 24" for a reference point. Add in a minimum 1' for the height of your pots. Then the height of your fixtures so say another 1'. Add those up and we have 4'. You only have 4' left over to grow plants with. So if you hit everything correctly with your stretch, you have only 24" from your canopy to the fixtures, and then the space in between the fixtures obviously. We all know warm air rises. So that "cushion" space you have left over for air to circulate and rise is minimal to say the least. This means your have zero wiggle room. The bonus of having lots of space within your room(s) is that you have more of a buffer zone for temps. No space = temp / humidity levels that drastically spike with the drop of a hat. The bigger the room, ceiling height, and space not being used by lights, the slower these factors will rise.
It's honestly a pain in the ass it is to have a room jam packed with plants and not have any wiggle room to access them. It's doable dont get me wrong, it's just a nightmare once the plants get bigger.. I've run a few rooms early on where I did this and ended up having to carry half the plants out into the lung room just to be able to access the plants at the back of the room. Be prepared for this and know well ahead of time how you will train and support the branches once they are loaded with buds, and how you plan to access the room to water. Pots of soil with tomato cages seems to be the most viable option for being able to support and move shit around but that's just my opinion. That being said, how will you collect your run off? Food for thought.
As for power, your going to have multiple wall fans, inline fans, and lights so make sure you have the capacity for everything prior to installing your panel. Good idea to have a plan for humidity levels during lights off, especially during flower. Regardless of what setup you decide to do, you have 2 options to deal with the humidity. You can run your filter and inline fan all night (or on an inkbird humidity controller) but that will still draw the cold air in from the lung room. If you do that you either need to now heat the lung room up using a space heater or juggling your homes thermostat. I wouldn't advise putting the heater in the grow room unless you have it setup to not roast the plants. Better to have it outside and make the temp transition less intense. This is an added cost regardless of how you look at it. Take into consideration that high levels of humidity will fuck the carbon in your filter at an accelerated rate. The heat produced by the heater in the lung room would dry the air though which would help balance the humidity inside the flower room.
The other option is to have a properly sized dehumidifier in the room. That's going to add some heat, as well as extra cost onto your power bill.
Sorry for another novel. Hard to put this all into point form.