I also bought the NUX and have been playing around with it. I find it to be a very useful and versatile tool. It has a built in USB audio interface and there is an ASIO-Windows driver for it. Running a long USB cable between the NUX and the PC, allows me to monitor the backing track and my own playing on the PC speakers and also record myself. You can also monitor on headphones plugged into the NUX.
The “Mightier Amp” for Android is nice in that it allows you to have more presets for bass. (Releases · tuntorius/mightier_amp · GitHub). The official NUX “MightyAmp” app has 3 bass and 4 guitar presets. The “MightierAmp” allows you to use all 7 presets with any of the Gate, EFX, Amp, IR, Mod, Delay, Reverb… so you I have 7 presets for my bass saved on the plug. Its fun exploring all the sounds my bass ukulele can make!
BTW: I think the latency that @JerryP mentioned is a problem on the bluetooth implementation. The usb seems fine… but obviously you are then connected by a cable to the PC.
Another minor niggle is that Linux does not recognize the audio interface. I believe that is fixed in kernel 5.12 … but that’s a bit too cutting edge for me!