My favorite topic....
The science around RV navigation is a double-edged sword. You need it but it can make life miserable for you at the same time.
Firstly, reliable programming on the GPS itself is near impossible. The interface is not meant to plan a trip with multiple stops. You have to train yourself to think Point A - Point B and that's it. Even if point B is a gas station or stop along the way. There is no Point C.
Secondly, look at the route carefully. Check route using a 2nd reference, possibly a 3rd. I use the Rand McNally truckers map (laminated) to verify at a 20,000'view, then use Google Earth to get down to the side road details.
Thirdly, and most importantly, Do not expect to buy a software package to set up your trips and then export to your GPS. Nothing but a pit of frustration. They all do a great job at selling, poor in practice.
So, that said, I have a Garmin 760LMT. It works OK, does not crash, but not 100% reliable. For example, I am at an RV resort right now that is 200' from the highway. There is an on-ramp at the highway going North. This exit is famous as a truck stop. Garmin has me going south on the highway for 2 miles and turn around to go north, go right past the ramp I should have taken in the first place. It has done this 3 other times in different places. Almost like Garmin does not recognize the northbound ramp. In July, took me down a side road with a 4 ton limit. I have a 46,000lb MH.
All I can say is that, from what I have read, it is better than the rest!
Good Luck!