Ok, I have read the posts and will give my honest two cents. My early experience is Photos grown outside. My nature is to run after the best new thing, in the cannabis world the newest plants or cultivars are Autoflowers (Freakshow by Humboldt seed company is a mutation) so like others I chased this new thing to learn about it. I started with Mephisto strains, first year yields were terrible, problem with autos I learned is in Veg, they have a genetic predetermined time to flower, you as the grower cannot control this like photos. This leads to limited ability to fully mature in vegetation in my experience. I feel pot size is irrelevant to yield, you only have 60-80 days of plant life why spend 30 days growing roots and have a 12 inch plant going into flower.
Now like others I tried 3,5,10 gallon pots but did not increase yield, I had huge root balls two and a half foot tall plants after stretch maybe. Some would shoot up, lanky long internode length, maybe harvesting 2oz. the high side.(Early on some of Mephisto strains had huge variations some plants were tall some short, they are more stable now).
The highest yields were in 2 gallon pots, in coco and worm castings only, no perlite. Watered to runoff, once a day up to 30 days increased to twice a day after that. Cannabis grown in coco should be viewed as if you are growing in hydroponics the more water the faster it grows, coco is not soil, it is more like a wick or a sponge, it soaks up water and the roots wick it away. In my experience you cannot over water coco, PH stability in coco is by far the greatest way to improve yields and over all fast veg growth. Vegetation growth should be your main goal with autos.
Another aspect is over feeding, huge amounts of nutrients will not always grow the biggest plant, I always tell my son when he looks in the tent that I’m not trying to grow leaves and stems, I’m growing buds. Autos do not need nutrients like photos do, they need enough is all. In my experience I watch the Nitrogen, why? Many nutrients overuse it, for instance Cal/Mag the go to fix all stuff, all or most have nitrogen, perhaps just 1% (exceptions: I use Roots Organics cal\mag which has no nitrogen) autos don’t need all that N they are not in veg long enough to benefit from it. Even amounts of NKP in the first 30-50 days until complete flower set, any flower nutrients or high KP before this are yield killers. I do use Roots Organics Oregonism XL similar to recharge for a overall health enhancer top dressed every other week for first 60 days, I also use Roots Organics Soul Line as my base nutrients on all my plants, garden plants, house plants all, for years now. I’m very familiar with it and use it on a variety of plants. ( no, I don’t work or have affiliation with the company) I like their products that’s all cuz they work for me and my environment. After flower set I change over to flower nutrients until they finish. Another thing about PH, autos like PH in veg in coco a little lower than the standard 6.5 I can get great growth with 6.0-6.3 PH in the first 30-50 days the slowly raise it to 6.5, i water to flood every time, in coco salts build up daily, you need to flush that out or your PH at root level will suffer and yield will suffer, with autos you cannot switch back the lights and put them back in veg like photos. Once you affect growth in veg with autos in any way the setback will be in flower.
Another technique, I do not top autos, I pinch leaves that cover bud sites in veg then when flower sets, I remove all bud sites below the first 12 inches of the plants, and any sucker branches. Why do this? to slow it down a bit, kinda shocks it for a day or two, also only the top best bud sites are left for flower production, this causes the plant to focus on only the flowers left, they get maximum light and nutrients it can double yield this way.
I use QB boards HLG the brand I prefer they produce very little heat, which can kill yield, some I have read seem to think heat plays a factor in growth and yield but you have to understand leaf temperatures to grasp why you need to raise the heat when using LEDs my autoflower tent runs at 85-87 thoughout the daytime lights on, some say this is to hot, in the early days of streetlight MH grows I would run temps as high as 90 with no burnt tops or wilted plants, it’s all in ventilation and air movement. As long as you have air movement in the tent, and air exchange, inlet-outlet plants will do just fine. I also keep a fan running in the tent during lights out, this I feel keeps humidity even while the plant is utilizing its daylong stored nutrients. I run a 18 on 6 off light schedule until it’s week 4 of flower, then I switch the lights to a 16 on 8 off schedule. Why? Well I found some autos would not flower or some would not finish completely so like with photos, it forces them to, with autos it also slows down flowering, and mimics nature’s waning light, this I found can increase size and density of the flowers. Not in all cases cuz plants like humans are individuals every one’s different.
Well that’s my two cents of experience on autoflowers, I still prefer photo period plants, but I’m a sucker for new trends.