Rate mode is not allowed combined with CruiseControl, this start config alarm.
And Yes, CruiseControl add a little more CPU load because more calc is done for thrust / angle.
If you want to do the flip you should cut motors at angle > 90°, just keep default settings.
The PowerDelayComp is also taken in account so if if you a too small MaxAngle flip is not finalized maybe.
You can see Throttle curve in Vehicle tab, previously the max was set to 0.9 (90%)
Did you successfully follow previous step i posted ?