Having had a Garmin Edge Touring Plus and recent got a Wahoo ELEMNT – I can recommend Komoot for route planning both on and off road. Though I do confess that some bridleways seem to be missing from the Komoot mapping in the UK. They do use OpenMap so some community editing would pay off for many.
I have really tried to like BaseCamp from Garmin, for road, for touring, for MTB, for multi-day vehicle drives. And in conclusion, I find it frustrating, slow, cumbersome and I try not to use it at all. I have also downloaded, converted and inserted into BaseCamp OpenMap based maps.
I have used cycle.travel website which has some great multi-day tours (eg Lon Llas, Coast to Coast).
I have also used TCX and GPX to transfer between different apps. I now take an approach of planning in Komoot and transferring to the ELEMNT is very easy but the Edge Touring Plus is more of a file copy.
Strava seems OK for road. RideWithGPS also Ok. The ELEMNT records and transfers into Strava, Komoot, RideWithGPS. Much more easily than my Garmin which is a USB connection and upload.
Most of these rely on OpenStreetMaps (OSM) and its variations, which covers both UK and overseas. Beyond that then each have their own strengths and weaknesses and it depends what you want to do.