Get one that's 4K (or better nowadays). If you can't read a license Plate, it never happened.
We have the Rov R2-4K cam. It records in a loop over writing the oldest recording first.
Get the biggest memory card it will take to hold as many hours as you can at 4K density.
We use the Rove 4k as well on the tow rig, I also have the Garmin Mini in the back window. We use the Garmin in our other vehicles. The Rove is nice, easy to set up, has time, date, location, speed stamps in the video as well.