Can pretty much tell how stronger your getting by the way the training is going. No need to gauge by a single rep max, but kind of fun anyway. Maybe every 3 weeks, or so for most people. A couple of guy's were squatting so I joined in for a few sets. After my regular workout I loaded up the PR for a few sets of overhead presses.
The following is what works best for me, may not be suited for everyone: Best gains by far were/are from partial PowerRack (PR) training. Get to hit all three phases of a muscle contraction, from the weakest to the strongest, at the most effective (max for reps) weight. That's what the original concept for the Art Jones machines were for. His cam gear designed , in my view, changed the whole idea of machine training.
Second form of best gain training were heavy 20 rep (or more) breathing (3 to 8 breaths between reps) squats. Also used DL and power cleans on this form of training.
A close third. are Rest-Pause training. Usually between 10 to 15 seconds between reps. Use only the Big Boy exercises like heavy compound squuats, DL's, bench's, pulls, presses, etc.
Throw in 5X5's as right up there for good gains. Good Luck.