I would do 4 autos in that space. I would do 3 of one strain and 1 of another. I say 3 and 1 cause you can have variety and if they are different in a big way it is easier to accommodate one plant that is different than a group with multiple differences.
As far as an auto hermie-ing, good luck. It rarely happens.
Autos are fun. They have their time and place. True, they might not produce the top shelf stuff but in my experience they can be as good or better than the "dro" you get on the street. I hate that term "dro". I recommend growing autos for your first grow, you WILL learn a lot from them.
I grow perpetual photos but every summer I do an auto grow. Last summer I pulled 13.83 oz dried and cured from 3, yes 3, sweet seeds cream mandarins. That was in 3 gal smart pots, soilless, in a 22x24 inch space with a 400w. Nice smoke too. I did more than just those 3 that grow, but those were my best autos so far.
I hope that when your lady sees the true and natural beauty of this plant she will understand that it is not something bad and will grow to love the plant for what it is. Get her involved in the grow so she can have the feeling of being part if something great. Grow some flowers for her next to the weed plants and when you talk, and or brag, about the plants always make sure to seem more proud of the ones you are doing for HER! I know how it is with a wife. My wife is a pediatrician and was worried about me doing something like this in our home here in the south where they still hang people for growing. Not that she is anti-cannabis, she smokes more than me, but she was worried. Now she has her own plants and it all started with roses for my first grow.
Good luck, grow hard, and above all, HAVE FUN.
If there is anything I can do to help let me know, my door is always open.
Polo