Looks like if no mode is selected, then it defaults to "air/acro" mode. And after some more time playing around in cleanflight and with the transmitter, it seems like my 6th channel just isn't connected to the FC???
Channel 5 works fine with all 4 switches (tested all 4 to make sure it wasn't a wiring issue with Swc A,B, or D on transmitter) even could confirm to see the slider/indicator change in cleanflight. However when setting any of the other switches to channel 6, nothing seems to happen (in cleanflight or on the quad) like it does with channel 5.
Even was able to get Swc C on ch. 5 to work as an arm switch, I didn't keep it set this way and reverted back to Swc C for flight modes, but more was just testing for my own understanding on how the arm switch would end up working.
I'm guessing it's safe to assume, without digging into the quad and confirming that Ch. 6 isn't connected, and then actually getting it wired in, I'm either stuck with 1 flight mode (acro) and an arm switch... or I arm the motors with the throttle stick, and can switch between flight modes?