Onewheel Pint! It was the ultimate quarantine toy. I saw so much of my city I hadn't seen before and it did a great job of getting me outside in general.
On a charge, 15 miles but depends on your weight and the terrain. My son put 22 miles on one once on a single charge.
Safety wise, yeah wrecks on onewheels can be bad. If you are a speed demon you will break something. If you are careful you should be fine. A set of fangs on the board and a pair of wrist guards are highly recommended. And a helmet at all times.
The safety is what put me off of those. Read a few too many stories about permanent, serious injuries to young people using them (relatively) safely. It does look like a ton of fun though.