All good advice, and ultimately yeah, "you do you" always applies. Getting on target faster, practicing breathing and dry firing, for sure helpful. And I definitely did have a flinch when all I shot were "full-sized" cartridges out of light hunting rifles.
I'm a pretty mediocre shot, trying to improve, but adding a 223 trainer was pretty huge for me. The lack of recoil helped me eliminate the flinch, and honestly just got me to practice more. Dry firing is great, but having the 223 is more like I can get "dry fire" practice with instant feedback to keep me more honest. Hitting steel with the 223 is fun enough that I want to shoot more, and that feedback loop leads to more shooting, which is maybe what it's all about.
A 308 trainer isn't a bad idea though, I might consider that to mix it up. I view it all as a toolbox now. I still shoot 22LR, it's cheap and fun and I can work on group sizes from field positions for dirt cheap. I might shoot 100 rounds of 22, 50 rounds of 223, and 5 to 10 rounds from my main hunting rifle as a solid practice session. As season approaches, I'll mostly shoot the main hunting rifle.