I own XP2 Pro for a couple of months and can say several words. First, it's a great product that has no competitors for those price point. BTR5 and UP4 have much less power (I don't want to spend extra $70 for a balance cable for my HE-400i 2020), Q5S costs three times the price.
The sound is excellent: punchy on high level and more airy on low one.
BUT
Bluetooth died after a month of use, so I asked XDuoo for a replacement and waiting for a delivery from China. I found a lot of complaints on XDuoo's forum about the same issue
SO
I guess XDuoo had or have had some issues, that's why it's not so popular yet.
Furthermore, I hope the problem will solve and if it's not. Oh gosh, BEWARE!
If it's not, I will go for BTR5 with balanced wire :(