Andrew,
Welcome to the wonderful world of CW! I've just jumped back in this year after a 20+ year hiatus.
The QMX (mine's not a +) is a fabulous CW machine.
Good job getting your voltage at 12v or less. It sounds like you have all the pieces put together.
As long as you don't transmit (don't plug in a key), I don't think there's any possibility whatsoever of hurting it. Listen away with any random antenna connected.
I've been using a home-brewed EFHW for 10/17/20/40 on the vast majority of my pota activations. I cut it to be as resonant as possible: under 1.5:1 on most deployments. I use it without a tuner. With each new antenna installation I do use the QMX's built-in SWR check to verify everything is where it should be. Occasionally this has prompted me to re-adjust how the antenna is hung or how taut it is. Having the built-in SWR protection is nice, though occasionally I turn it off when windy conditions give me little transients that trip the protection.??
With nearly 1000 QSO's so far this year, the QMX is doing terrific: no issues. It is a durable little machine with only a little care.
Early on, I had several local friends encouraging me to step past my anxiety and throw out some calls. I highly recommend Parks on the Air (pota.app). It's usually very scripted, and people are out there wanting to hear from you.?
This was an encouraging primer:
But the most fun way to get started is to find a local buddy and do a joint activation. The encouragement and advice is invaluable.
GL es 73 de Todd W2TEF
Todd W2TEF