"Best" mic for Dirac Live

[Sal1950]

I would point the UMIK-1 mic at the ceiling in each spot for a Dirac calibration, correct?

Yes

Just happened to think... what about when Dirac gets to my 4 ceiling Atmos channels? Do I turn the mic parallel to the floor for those measurements?

No

Yes, and use the "90 degree" cal file.

Yep
With Dirac you are attempting to do in-room response measurements at the MLP.

Now OTOH if you were trying to measure the speaker or it's individual drivers, you point the mic directly at the speaker closely at like 6" to eliminate the room and use the horizontal/direct calibration file. Lot's and lot's of if, and's and but's here and I am by far no expert.