I find naming feedrate as a percentage to be quite odd. Percentage of what?
Feedrate is going to be dependant of the ability of a given machine, but there IS some scientific baseline to work from. It does take a little math to figure it out. It's not hard or complicated but it is math and not just a guess. As a person gets more experienced, a tongue in cheek, is really not so, but an educated assessment of feetrate.
The rule of thumb I like is -- you want to make chips, not dust. Dust means feedrate is too low.
Another is - if the cutter is smoking, getting discolored or burning --- the RPM is too high.
Feedrate is calculated by getting a chipload rating from a tool manufacturer, then multiple by number of cutting edges (flutes).
https://www.guhdo.com/chipload-calculatorThere are LOTS of calculators out there - this one is nice because you can change RPM or feedrate until you get a decent CHIPLOAD.
Soooo - FEEDRATE - is NOT the only concern. You need to figure out CHIPLOAD, RPM, number of flutes, to get the proper "feedrate". AND - you need to match all that to your particular machine.
You CAN reduce the chipload by varying the RPM and feedrate to adjust your chipload. If your machine is complaining, you can adjust further to reduce the chipload.
A tiny bit of algebra A+B=C You could say 5+2=7 OR 4+3=7 OR 6+1=7 The combination of numbers really need to add up to something. That is how feedrate works, but it works with RPM and number of flutes and comes out to chipload.
Keep in mind - in wood - you do not want 4 flute cutters, and single flute cutters work great. It's all about allowing the chips to evacuate. It's also to allow the chipload calculation to work to your favor in case you need to reduce the number of flutes.
I do hope this helps a little.