How many plants should I grow?

Since they are autos I would only do one, it of course depends on the Fast Bud strains you selected and growing medium. Some autos can be small. I would also recommend if you are doing more than one plant to use the 7L pots as it will limit the size of the plants, go with the 11L if you decide to grow one plant. You could always start two and select the one with the best growth to finish in the tent and simply move the other outside or by a window to finish, in that case I would use the 11L pots. I have two autos in 5 gallon pots that are overflowing a 60x120cm tent. You can check my diary to get an idea of the size. You will may also want to consider LST, Top or FIM to help control the height/size. Best of luck!