From what I understand going more in depth requires either maxing out your HR (Steve House describes how you can do this in Training for the New Alpinism - basically sprinting uphill until you collapse, seems really unpleasant) or doing lactate testing in a lab.
After running my first 5k race all-out, I recalculated my training zones based on a max of 205 instead of the 190 that the apps had estimated for me, and things started to make a lot more sense.
Also, max heart rate is only useful after you've been running for awhile. If your body hasn't started adapting to the change, MHR doesn't do much and often inaccurate. It's like 1RM in lifting, 1RM is meaningless in beginners as their bodies and central nervous systems haven't learned to fire all the muscles yet.
100%, don’t geek out in the beginning just run at a slow pace until it’s comfortable and several consistent months in tinker around
https://uphillathlete.com/aerobic-training/aerobic-anaerobic...
Unless you're used to reaching your max HR during exercise - something I don't suggest - it will be painful, but you're not supposed to hold your heart rate at this level for long either, just long enough for the heart rate sensor to register that level.