I haven't found protein to really change muscle gain, I did high and low protein. Majority of days I'd be maybe 60-80gm protein. Still put on 10kg. I dieted on high care, low pro, low fat and it worked fine. Things like that I tried.
However training methods seem to impact things the most. I took a leaf out of my cycling training where diet was never really strict from coaches (I paid top people) but the training load was the be all end.all. All formulated. You Had to do the training and you Had to hit.specific.numbers.
There is millions of.dollars, doping, lab testing thrown at cycling. These guys know.
So I hit heaps of volume. Upper body 3x a week, lower 2x. Weights very low, reps 12-15, rest time low, I drip with sweat every workout. I never.go near failure, I feel fatigued after training.but never destroyed or.fried if that makes sense.
That has been the biggest factor so far. So it's things like that which I mean to try out. Everyone is different and what we tell ourselves is working might actually not work as good as something different.