Are 5 gallon air pots big enough before transplant in late July early August into 30 gallon containers of stated In mid may

What's your latitude and climate type? If you grow in your own garden and have easy access to the plants, you can just grow in 5 gallon pots, they're also possible to move around, 30 gallon pots, not so much :) Growing at 55° North, wet coastal climate, I start in 1 gallon ish pots indoors or in a greenhouse around 1st of April and plant them outdoors in final pots or in the ground 1st of May unless there's still frost at night, then I wait until the night frost ends. Photo plants topped multiple times, autos topped once at 3rd ish node. You have to pay attention to the weather pattern in the 8-12 weeks after fall equinox AKA first day of 12/12 (21st of September) where you grow, if it's humid and cold in October, you have to be very careful when selecting strains. You can get strains bred in this type of climate that initiate flowering at like 14-15 hours light and develop buds with an open structure that are highly mold resistant. Having a simple clear roof over the plants will help a lot in the battle against mold, a clear tarp works well. This reduces the amount of water from rain and dew on the plants while still having a great airflow. If you grow in a nice warm climate where it's still mild in November, you can basically just do whatever you like, start whenever you like, and grow most strains successfully :)

I've run my greenhouse in the outdoor season with 30+ plants in 5gal fabric pots. They work great and allow plenty of airflow to the root zone.

Its a big step up from peat pots to 5gal. I would go along the line of multiple transplants/up pots. Eg, peat pot to 1L to 1Gal to 3Gal to 5Gal to outdoors. I like to transplant into something that is 2-3 times the previous volume. This helps the root ball become nice and dense in the pot. Planting outdoors is great into earth if you have the option to do it. If not 30Gal is more then enough. Pants will need a light cycle of around 14/10 to prevent flowering from happening. This will not be possible with autoflowers you need to use photoperiod plants for an extended veg period.

I not exactly sure what size pot is best but probably bigger than smaller. I think your timing might be a little off as it is better to have your plants established before they sex and go into stretch which will start to happen outside around mid July. So I my guess final pot by July first. But I also live in a northern area so I have less time to get any plant outdoors. Hope this helps.