Well, I made the decision to go for Option #3 using the 12 volt to 24 volt DC-DC converter. I was sort of forced into the decision after doing quite a bit of testing of Option #1, using the raw battery voltage (~13.3 v).
I found that running at 13.3 volts, the CP5 control box was very sensitive to voltage fluctuations. If I applied power to the mount first and then turned on the (high end) NUC mount PC, the mount's power LED would immediately turn amber even just sitting at park. I could not slew at full speed either. The CP5 would indicate a motor stall during the high speed slews and show the amber LED again. The voltage fluctuation was short enough to not show up with my digital multimeter and was not detected by the battery monitor I use with the battery. (I did not bother hooking up an oscilloscope to see how long the voltage droop lasts but expect it is very short.)
So, I installed the 24 volt DC-DC converter. This solved the high speed slew issue and also the voltage fluctuation when powering on the NUC but introduced another issue I will need to solve. My interface to the battery is via a typical automotive 12 volt socket. The plug portion has just enough resistance in the spring loaded tip that it overheats when performing a long slew at 1800X. Doing several long slews in succession, I actually melted part of the plug without blowing the 10 Amp fuse in the plug tip. I will need to rework my battery box to provide a direct PowerPole connection bypassing the 12 v automotive socket to PowerPole pigtail adapter I am using for now.
The net of all that is that I will use the mount at 24 volts but will need to beef up my battery interface before using 1800X slews. For now, I'll use 1000X until I can wire in a dedicated 24 v PowerPole socket straight to the battery.