Welcome! All I can speak from is personal experience...all 2 months of it. I have a 2' X 4' X 5' tent. I have four 3 gallon smart pots under a 315 W LEC grow light. I also have a Dyson fan and my duct fan. My tallest plant (all autos) is 25" tall and I have a few inches to spare upwards. My plants are close together in the middle of the tent, getting the maximum light.
Both Obi-Wan and Troyzstang have valid points. If I had the room, I certainly would go bigger. I guess my contribution to your thread would be to go for the biggest tent you can accommodate. While you can always condense things within a big tent, you can't fit too many plants or equipment into a small one. Good luck!!