Hi @PJKIII,
Can you use the PoE ports on your MX for your MR34s? Sure can!
Should you? I would say that depends on your environment and if it makes sense. I would definitely offload wireless to the MR and off the MX. You'll have better functionality and insight for your wireless connections. I currently do not use the PoE on my MX for the access points, but that is only because of physical location, aesthetics, and the fact that I'm using a MS switch with PoE for those and other devices.
Found this helpful? Give me some Kudos! (click on the little up-arrow below) and If my reply solved your issue, please mark it as a solution 🙂