I've used several bluetooth mice (mainly logitech and microsoft mice), as well as usb based ones (wireless dongle) with a micro to usb-a cable.
Android picks up that it's there, shows the cursor and all is good. The OS isn't really polished for mouse use, so some things may seem... odd.
The Logitech T630 ultrathin works justs great via bluetooth. It has a nice feature in that it has a switch underneath so that it can remember two different devices it is paired with. Position 1 for my laptop, position 2 for the Pixel C. It's really nice for light editing in Google Docs, Sheets, or Slides.
Does it connect via the device bluetooth or does it come with a little wireless dongle?
Connects via bluetooth radio. No dongle.