RE: Different Z lead screw travel between MK4S upgrade screws and Core One kit — 2 mm mismatch
I did it by homing and moving the X-carriage (from menu) (nozzle on the left and back center) and rotating the spindle so that the nozzle touches, and then everything is level... there's nothing you can do, one driver is causing problems, we need 3 drivers, then move all 3 spindles and hom... then you'll have everything level.
If you are talking about a "static" tilt (which is due to a tilt between the printer's base plate and the CoreXY plane), you can correct that by adjusting the mechanical bottom end stops near the three lead screws. Either insert M3 screws into the three tapped holes in the base plate, or use plastic shims of suitable thickness around the lead screws. (There are various models on Printables.) Then the Z calibration, which drives the bed into the bottom stops, can make the bed parallel to the CoreXY plane, and you don't have to readjust manually after a Z calibration.
But if the pitch of the three lead screws is not the same, then neither your method nor the one I described can fix this.
RE:
I did it by homing and moving the X-carriage (from menu) (nozzle on the left and back center) and rotating the spindle so that the nozzle touches, and then everything is level... there's nothing you can do, one driver is causing problems, we need 3 drivers, then move all 3 spindles and hom... then you'll have everything level.
If you are talking about a "static" tilt (which is due to a tilt between the printer's base plate and the CoreXY plane), you can correct that by adjusting the mechanical bottom end stops near the three lead screws. Either insert M3 screws into the three tapped holes in the base plate, or use plastic shims of suitable thickness around the lead screws. (There are various models on Printables.) Then the Z calibration, which drives the bed into the bottom stops, can make the bed parallel to the CoreXY plane, and you don't have to readjust manually after a Z calibration.
But if the pitch of the three lead screws is not the same, then neither your method nor the one I described can fix this.
I've got the shims in my printer just as a crude improvement over the obviously non-aligned default endstops. The M3 screws are a good idea, just make sure nothing gets overstretched (there is quite a bit of leverage as the screw is > 40 mm away from the spindle. If it works, great, I didn't like the tension when it runs into the endstops during calibration.
In everyday operation I always keep it level it by manual spindle adjustment per the quote. Just routine diligence, it avoids skew between X, Y with the Z axis (in theory - I'm not claiming to print anything where you'd notice).
Printers with three and four individually controllable motors do exist but of course someone needs to pay for it. But honestly, I always thought I had paid enough - when I understood the Original Prusa approach with co-wired steppers I didn't know whether to laugh or cry...