If you have an OnTheGo (OTG) enabled phone or tablet you have that option with your current Garmin.
Plot a route on whatever app/website you like on your phone or tablet (easier said than done!), save it as gpx/tcx and using a cable transfer from your phone to your gps device.
What this means is that by using OSMand (with maps already downloaded onto the phone/tablet) you can plot routes on the fly without needing an internet connection. Total independence!
The big advantage of a Wahoo is that you can do this via Bluetooth from the Wahoo phone app, but, you need an internet connection to process the new route in the app.
The disadvantage of Wahoo is that while you can transfer a file via cable from PC to unit, you cannot do it from phone/tablet to unit - or at least I haven't been able to do it.
Just remember, plotting routes on a phone or tablet can be a frustrating job!