I use Co-Pilot RV app on a tablet. It lets you set the type of road and RV parameters. If you get a GPS, it does one thing. If you get a tablet, you can run multiple useful apps like Waze, Allstays, and RV Parky.
My wife uses the TomTom we bought for the first RV we had. It tries to take us down some scary places sometimes. Always back up the GPS with a good map or Google maps of the route. I like Google maps because you can go to satellite and street view and see what the entrance to gas stations look like.
And you're correct, this topic has been discussed several times. At the top of the page, type 'rv gps' into the search box. There are 5 pages of threads to view.