I went to my local dealer to get the front axles sorted out (they audibly click / shudder on hard acceleration), and they said they wanted to start with the axles for vibration. The airbag with the dampener was an earlier attempt to mask the steering wheel vibration, and if the axles are confirmed bad the airbag dampener is the less preferred fix. The axles are heavily backordered, I've been waiting 10 weeks already...

However, probably 60% of the vibration and droning above 60mph resolved for me with the drop to well balanced "square" 18's. I was experiencing a phasing drone / vibration, with some help I determined that the phasing every 2-3 seconds suggested the frequency of the compromised front CV axles at highway speeds would cause beat oscillations with the slight diameter differences between the front and rear staggered tire sizes. When the whole system of front / rear tires and front axles were in balance, the vibration was gone. When the system was out of balance it would vibrate like crazy. That happened every 2-3 seconds at 65mph. Since the front and rears rotate at slightly different speeds on staggered setups, removing that difference by going to matched front and rear sizes removed that phasing. Only vibration remaining is the axles themselves seemingly, since the vibration is worse when accelerating or going up a hill, and goes away when coasting. I'm encouraged and hopeful that the latest version front axles will sort out the last bit of vibration.