Congrats on the shinies, and thank you for reporting your findings!
Here are a few thoughts
Indeed, usually one needs to choose between regular toolpaths at low DOC, high WOC, and moderate feedrate, and adaptive toolpaths at high DOC, low WOC and higher feedrate.
I guess you already know about that series of videos, the second one is of particular interest since it’s about using 278Z in aluminium. Winston’s recommended DOC for profile cut (slotting) is 0.38mm / 0.015", that’s 6% of the endmill diameter, which matches the guideline I usually follow (5 to 10% of diameter)
You can use a loupe to check the tip of your endmill, it may have been chipped (and then indeed, plunging won’t be fun). I avoid straight plunging as often as I can, helical or at least linear ramping helps a lot.
To reap the benefits of adaptive clearing, I guess you could go up to 6mm DOC, and I would personally reduce that stepover to somewhere below 1mm, and push the feedrate higher (HSM style)
What diameter were you boring ? It might be beneficial to use a smaller endmill and to a regular pocketing op, that way you’ll benefit from helical ramping, and then adaptive.
For comparison in the 278Z video, Winston uses 18K RPM and 914mm/min but at half the DOC (0.38mm). You end up having a similar chipload with your settings. Slotting will always be hard(er), and an air blast will help a lot.
1mm sounds a bit high to my taste for a facing operation ?
Also, 24k@850mm/min on a 3-flute is a 0.0005" chipload, near the lower limit, I would probably go 100% faster and 50% shallower