Ah well i can try! Only had the i3 since start of january, got it as a kit and built it myself. Was rather confused by it all at first, particularly the marlin settings. Found a lot of examples settings online but no explanation as to why they should be those values so found your write ups extremely useful.

So using your values as a proven baseline i did some experimenting although i was never great at experimental write ups... So ill go through the settings and try to explain how i arrived at the values.

HOMING_FEEDRATE - I've kept same as your settings recap post

DEFAULT_MAX_FEEDRATE {400, 400, 2, 200} I know the x and y speed seems excessive but i haven't noticed any skipping. I know you've done the math but I'm a rebel I also have a direct drive extruder which seems to be pretty strong and i haven't had any skipping or grinding issues at this speed either. Although I don't print at over 90mm/s, with travel moves set at 250mm/s.

DEFAULT_MAX_ACCELERATION {6000,4500,400,500} I've experimented with different acceleration settings to try to deal with ringing (ripples) and found that for me, higher max acceleration combined with higher default acceleration made the ripples less noticeable. Or at least it seems that way. Y acceleration is set lower than x as the print bed is 6mm aluminium with a glass plate and seemed like a good idea to have it set lower.
DEFAULT_ACCELERATION 2000 Set any higher and y starts to skip steps, on travel moves i think, as they're the fastest.
DEFAULT_RETRACT_ACCELERATION 1000
DEFAULT_XYJERK 30
DEFAULT_ZJERK 10
DEFAULT_EJERK 10

I haven't done any proper experimenting to try to figure out what affects ringing, but turning acceleration up seemed to have worked some for me. Im printing out an adjustable x belt tensioner so i can easily adjust the belt to see how it affects the ripples. I feel like the key is figuring out a balance between print speed, default acceleration and jerk settings. What annoys me the most aren't the ripples but intact corners,slightly protruding, as if the filament kept flowing in one direction as the print path turned 90 degrees. Turning down the jerk settings leaves the corners less sharp, the only other options seems like printing slower so will try that next.