#1 & #2 were answered by the owner as he asked the square footage for this condo. (I had to get out my papers from the Association for the first. #2 was told to me that it's part of the code for Florida.) His estimates were for the right sized model for condo units.
I don't know about the electrical part; I leave that up to them. (If he was coming up this weekend, I'd ask my eldest Bro as he has built a house from the ground up before.)
I will Google each unit to see if which one is the best; if it's the first company's unit, I am going to add a 10-year warranty (on top of the manufacturer's) so that if anything goes wrong later because of when they installed it, I won't have to pay a cent for them to come out & fix it.