im not a pro indoor grower so im gonna avoid some questions but... you should start with at least 3 plants. you can look at as :
33%=male
33%=female
33%= hermie

hermies arent too common but you have just as good a chance of getting one. You dont have to worry about your closet getting cramp for the first couple weeks, you just need to grow until around preflowering or whenever you plants will show sex, then get rid of the males and hermies unless you want to use them? Out of three you will porbably get 1 or 2 females. I've grown a little without mylar so im sure if it increases yield but it really helps get light to all parts of your plant. You just need enough fan power to get some circulation in the air. With most strains the ordor will become noticable... probably around flowering time. I'm not 100% about the fan and the soil thing, Goodluck.