Having just gone through all of this with my recent upgrade to the 385, I have some comments.
Use Rob's default settings as a starting point.
Fly with the AP in track mode. Manually turn the knob left and right 90 degrees. Adjust until the turns stop about 1 degree from the intended course. Watch the vertical during the turns to ensure a stable altitude. I was able to dial in the turns spot on, but not the altitude, but I got it close.
Then repeat the same tasks, except have the EFIS in heading and altitude mode. Turn the heading bug and make the EFIS setting adjustments until you get the desired results.
If you turn some of the gains up too high, you will get some very aggressive maneuvers.
Also, on the 385, make sure you set the altimeter setting before every flight. It's not a big deal with the EFIS in control, but your altitude will be off if you're in AP mode only.