Sounds like the strings you are using are too low tension. They may be easy to play but the trade off is that they will be quieter, less defined and buzz occasionaly.
Totally recomend the Line 6 stuff.
The G30 never failed and G70, now discontinued, still has more features than any other unit out there.
Any digital wireless works fine with
Piezo or mag pickups.
Its a great bit of kit but screams out for a couple of improvements.
The tuner should be accessed by a long press on the footswitch with the A/B function a quick press.
Also a USB charging port should have been put in the power lead.
HX works very well with piezo on upright. Especially when you load some Impulse Responses from 3Sigma Audio.
In the end there are too many oportunities to tweak parameters on the HX, drove me mad.
I've tried 10s 12s & 15s for upright over many years. 12s definetly work best on upright.
But more important than any amp or cab is strings and pickup choice.
Thats 80% of the sound.