I cannot stress enough how important good lighting is. Your lighting is the most important aspect your your grow and trying to scrimp on light is a HUGE mistake. If you really want to do this right, you are going to want to go to HPS for flowering. I would not use T5s all the way through. If you are unable to buy both a T5 for vegging and an HPS for flowering, I would get a digital ballast that would run both MH and HPS and use the MH for vegging. The bottom line is that, while you can grow with T5s all the way through, it is going to cost you more in electricity and you will end up with less bud than if you went with an HID, sometimes a lot less. Also the initial cost of enough T5 tubes for a 4 x 4 will run more money than an HID set-up. Just so you know, you would need an absolute minimum of 80,000 lumens to flower in a 4 x 4 space and most people run more. That is 16 tubes emitting 5000 lumen or 2 8 bulb fixtures. Vegging and flowering use different spectrums of lights, which is also a consideration. You will need to swap out at least some of the blue tubes for red tubes to flower. And will probably put out more heat, as you will need a lot more watts with T5s than HPS. An air coolable hood or cool tube makes the HIDs easier to cool (and I would never buy a hood that wasn't air coolable).
How much money do you have to spend on this? That is an important question and can really help us get you going. You are also going to need a fan and filter. Depending on whether you go with a 2 x 4 or a 4 x 4, this will run $100-160. Seeds, pots, medium, nutrients, surge protectors, timers, fan speed controller, and miscellaneous will also start to add up. Cannabis IS finicky and demanding. There is a huge amount to learn. You can only keep it simple to a small degree. I have been growing for decades and I still learn new stuff all the time.
Who is the reputable breeder that you are getting seeds from? If it is someone you have heard of locally, be very cautious. Breeding good stable gear takes generations and careful selection of parents. I am very picky about who I buy seeds from. This is a 4 month process and you generally don't know until the end of the 4 months whether you have gotten gold or garbage.
I am thinking that you do not really understand how the ventilation/exhaust works. It is actually the exhaust pulling air out of your space that will allow new fresh air to enter the tent. Virtually all of us run passive intakes with good sized exhaust fans. The incoming air is going to be the temp and the RH of the air in the surrounding space unless you pull it from somewhere else (I pull my intake air from the crawl space). Where you exhaust is not an issue (unless neighbors can see it or it smells), it is your intake air that needs to be cool and the right RH.
Some of the things are pretty basic when setting up a space and not much room for discussion. You need a minimum of 3000 lumens (blue spectrum) per sq ft for flowering and 5000 for flowering (red spectrum). You need an exhaust fan with enough power to pull through a carbon filter and exchange the air in the space at least once every 2-3 minutes. I personally like to exchange the air more often. You will most likely need a carbon filter during flowering. You will need to research soil mixtures. You are not going to want to just go to your big box store and just randomly pick out a soil. Most soil need additives, like perlite. And you do not want anything with moisture crystals or fertilizer pellets in it. Try to stay away from Miracle Grow. You are also going to need nutrients formulated for cannabis. Decide whether you want to go organic or use chemical nutrients. You cannot really mix the 2. Then read up on whatever method you decide on.
Again, try to run proposed purchases by the people here and they will tell you whether what you are proposing will work and sometimes people have a source for the same thing cheaper somewhere else. Those of us that have grown for a long time have a bunch of equipment that we do not use anymore--either it was an ill thought out purchase or technology changed, which also happens. And this hobby is expensive enough without making stupid purchases....which all of us have probably done at one time or another.