Max heart rate is an interesting question. Would you necessarily have a fixed, permanent max? I’ve had days when I’ve gone RPE10 for 3-5min and maxed out at 195bpm, and times when I’ve held over 200bpm. I’ve seen 30-second bouts in my data where I’ve held 220bpm. If I do a kilo TT, I hit +190bpm within 30 seconds or less, and pretty sure I’m at my max by the end (~1:13).
My sense is that heart rate does not directly correlate to eliciting VO2max, but it’s a “pretty good” indicator.