QuinLED Dig Quad 12v to vExt?

I have a QuinLED Dig-Quad v3, that I will be using to control WS2815 strips of off a 12v LiFePO4 battery. My plan is to use the vExt input and Q1R port to control a relay that disconnects the main power input when the LEDs are off to save the battery from idle drain.

My understanding is the vExt input on my v3 board can handle up to 24v. Is the Q1R port voltage always 5V? Is there any reason I would need something other then a 5V relay? Would there be any advantage in terms of efficiency to using a buck converter to convert my 12V battery down to 5V prior to connecting to vExt?