When I'm in that phase of training, I cycle through 2-3 squat variations (usually less CNS-intensive ones like high bar, high bar paused, front squat, paused front squat, or squat from pins set at the bottom) and work up to a non-psyched max for the day. That's usually between 90-95% of a true max, based on general level of arousal and stimulant consumption. Most days I'd aim for a PR, but if a PR would require getting really pumped and grinding a near-max, I'd shut it down when I needed to and save it for another day.