I do not like any RV apps on a phone or tablet. I do not think they work as well when pulling a large RV such as mine.
Instead I have a dedicated RV GPS, a Garmin 785 RV with Traffic. This also incorporates a forward looking Dash Cam into the unit. What I like about this unit is that you input the trailer height, weight, number of axles, number of propane bottles and over all length of tow vehicle with trailer attached. You can also state no toll roads if you want to. I have never had any issues with this unit routing me incorrectly when I am towing my 5er.
2016 34RL CC; 2008 Ram Mega Cab 2500HD, 6.7L, 68RFE 6 speed, 4X4, Smarty S67, TDR 145K+miles