I often use the RWGPS with my Wahoo, true. The process is very easy because it is like "sharing" a route (you do not think in the GPX terms there); same for Garmin. However, I use the native feature of Wahoo called "Take me to..." as often. You just enter a street address or point at a map location in the ELEMNT Companion App, and the new route is being transferred to the device. No smartphone with you or no mobile internet coverage? Just use the "Pan & Scroll" feature on the device to get to your destination point. (I can hear touchscreen Garmins are even better in this respect).
Not for Wahoo. That is, you cannot plan your "Take me to..." route on a PC, for instance.
There is yet another remark. Both RWGPS and Wahoo are cycling related. Therefore, these will select bike-friendly routes, using bike paths whenever available. But you know the problem related to HS e-bikes well, Peter (my Vado is a 45 km/h e-bike). Technically speaking, you cannot ride a HS e-bike on bike paths in Europe (Denmark is the only exception). Therefore, whatever route planning system you have chosen, you won't be allowed on a road if an alternative bike friendly path exists. That causes some trouble for me as I know I am allowed to ride with the traffic but the app or the device are not aware of that...
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The segment marked blue is where HS e-bikes are allowed to travel. Bike route planners specifically disallow you riding there.