You can use either with its own usb dongle or directly on the usb BUT
i have not been able to use it with the “generic” dongle I use to connect to PC/table and
i have not been able to use both the “generic” dongle and the chocolate donge.
so my advise would be to spare money and not buy its bluetooth dongle. I have connected my dwarf to a small usb hub, and then a commercial bluetooth dongle to connect to th pc/tablet and the chocolate usb, which I plan to replace with a wifi one
On the latency… It is my first and only midi controller, i think it kind of works, but I am sure that is far from perfect on the sample rate of the expression pedal
it is not “simple”, but it is really customizable using an app (not on the play store…). You can find lot of details here