i have experience in this exact tent. I didnt do autos though, I vegged with a 400w did 6 plants in 3 gallon fabric pots (so i wouldnt have to transplant at all and no worry of getting root bound)
I vegged for 35 days and got complete BUSHES with the 400w. i topped each one a couple times which i would recoment not doing this more than 1 time if you plan to do 6 or more plants as they FILL UP SPACE FAST.
i switched them to a 600w hps to bloom and yeah, i even went down to 5 plants in the tent for blooming and there isnt an inch of spare space anywhere. they actually only fit in a very specific way lol. i switched them at 12-15 inches tall and they are peaking around 25-30 inches tall now 4 weeks in.
Hope this helps.