Those questions aren't really going to garner an "exact" answer. Commercial scale growing is more about turnover time than volume. More crops per year versus more per crop. It's all about how many crops can get done. Take a look at some of the "big guys" and they aren't growing for weight, but more for turnaround, 6 crops per year versus 4 gets them more total harvest.
Soil mix is entirely up,to you, there is no "this is the best to use" its dependent on your growing style. Some people like Fox Farms, some people like Pro-mix, some people run Hydro.
There is nothing different to be aware of growing in a greenhouse than there is in a basement, outdoors, closet, etc. They all have things that must be overcome, pests, powdery mildew, bud rot, nutrient deficiencies etc.
You say your "just into" the cannabis industry, and "planning" to start one??? Have a big bank account, and be prepared to lose money. There is a lot to "commercial" growing, license fees, METRC, electrical, buildings and so on. It's not "I'll build a green house, grow pot, sell it and make money. The industry that was getting $2500-$3000 a # is gone, and has now gone to $500-$600 #'s. A friend just stopped by a dispensary to get edibles for his wife, and they were chock full of $60 ounces, even "top shelf" was only getting $90-$110 an ounce, if you can make money growing in a greenhouse, by all means, have at it.