I've definitely seen a massive difference in training vs not. My first auto that started my love affair with them was a lone plant amongst photos in my tent. It grew to be around 5 feet tall, but was mostly one "decent" sized cola up top and some golf ball sized nugs. It's aggressive appearance however, FASCINATED me. So I started digging in deeper next round. Messed with LST and my harvest probably quadrupled. I was off to the races after that.
I'm trying to reach a method where most of the fruiting sites are only at the tops and the plant energy focuses there. It's not a difficult process. Mostly based on plant observation. Just some tying and training here and there, topping if you want. And cleaning the lower branches of clutter to eliminate anything down there that can mold, or just be a waste of energy = LARF I suppose.
But when I look at my plants, usually while I'm listening to vinyl, I often wonder if the particular plant genetics is predetermined to only give what it can give? Like maybe 5 tops would give the same amount as 20? It just get's "spread out differently". This is what I do when I'm HAF. So excuse me while I blather. I find the whole thing fascinating.