I struggle to understand aspects of this post. You've previously owned a Wahoo which failed. Have you contacted Wahoo about this? A complete failure is rare. The Wahoo does everything you want.
I use a Wahoo, RWGPS Premium and plan my routes in RWGPS and follow these on the Wahoo screen. It's very simple to do.
In the Wahoo app go to Settings >Authorised Apps >select RWGPS and follow the onscreen instructions. This is a one off operation.
Any route you create in RWGPS will be available in the Wahoo app. Select the route and it will instantly load on to the device.
Alternatively on the device go to Routes >Sync and all your routes will load to the device. This needs to be done whenever a new route is created. Selecting routes on the device is fiddly but if one pins a route in RWGPS it will be in the "Starred" folder and easy to find.
Why only use the Wahoo to record miles? It has all the features you need.