Hi. I can share my thought on some of these questions.
-2. Almost everybody starts with lettuce. It's quite forgiving and there is a lot of info available for diagnosing problems (lighting, nutrients, infections, etc) Leafy plants are the easiest to grow.
I haven't seen anything that can't be grown with aeroponics or hydroponics. Entire trees have been grown before. As long as you can support the plant it will work.
-6. Choosing what you want to control is a tricky decision. In a commercial hydroponic farm near me, their main controls are irrigation, CO2, humidity and ventilation. For an artificially lit system, I think the main controls should be light, irrigation, ventilation and solution cooling. Plants can keep themselves cool if well ventilated and heating is rarely required.
That farm that I mentioned mainly grows cucumbers, peppers and tomatoes. Hydroponics under glass.
-20. So far I've used Hydrogen Peroxide for cleaning the root chamber. I'm planning experiments with antibacterial coatings and UV light.
-21. The usual root chamber depth is 280mm. This is not for root vegetables. The root chambers for potatoes are around a metre deep.
-22. Aeroponics is more costly, harder to maintain and has a higher failure rate. Nozzles get clogged and need to be cleaned. Aeroponics systems sometimes have a hydroponics backup to mitigate risk.