Welcome to the forum. I am growing AHA right now and 3 should fit in there fine in 3 Gallon pots.
I went with the 3x3 tent becasue I wanted the 6 foot height so I’d have room for lights. Those 2x4 tents are designed more as veg tents, but they will work with autos
AHA flower quickly at about 4 weeks and LST doesn’t really agree with them. They will be fine without the LST.
@dbrn32 can address the lights with you
Depending on your budget GH makes a good product and is pretty much the least expensive. I use the big 3 from Fox farms myself with good results! The AHA will need nutes at week four when they start to bloom.
Hope this helps you out! Good Luck with your grow and i encourage you to do a grow journal so you can share your process with us and we can help you get and stay on track!
Make sure you get a pH meter and pH Up and Down and 7.0 calibration fluid. pH is the biggest issue we see with new growers.
All water and nutes need to be pH to 6.5 to keep them happy!
Also consider Cal-Mag given at one month and once a month there after, basically 2-3 times per grow. Autos seem to always come up a little deficient and the cal-mag will keep them growing well.