Sorry, I didn't find these questions in my search.
When tuning PID what is the preferable Max PWM? Do I want to find the highest Max PWM that no longer warns as overpowered or is it preferable to get as close as I can to 100% without failure? Also, if a P value was specified during auto tuning is it necessary to add the S parameter to the M307 line in config.g? I assume that we do but in the guide, it didn't specify. How important is the V parameter? The voltage is reported along with the other results of autotuning but isn't mentioned in the guide. The guide also instructs "run M500 to save the heater parameters in config-override.g (this is supported in firmware 1.17 and later)", but that file doesn't exist by default on my installation.
Further, is the P parameter persistent? I ran an autotune without the P parameter and M507 reported max PWM as 0.8. I had run one with P0.8 previously.
Most people tune at max PWM 1.0 (the default) and ignore the warning. But you can use lower PWM if you wish.
The P parameter you tune with gets carries over to the M307 parameters S value that are generated by the auto tune process, so it's persistent in that sense. If you edit config.g to have the correct M307 parameters after auto tuning, you should use that PWM value as the S parameter.
File config-override.g will be created when you run M500. But that file will only used if your config.g file includes M501 at or near the end. It's up to you whether you want to make use of config-override.g or not. It performs the same logical function as EEPROM does in 8-bit firmwares, and has the same disadvantages - i.e. changes you make elsewhere (in config.g) may get overridden by config-override.g.
Awesome, thank you!