Yes you will need maps of covering where you are going to if you want navigation. If you don’t want navigation then it doesn’t matter. It depends on where you are going and what maps you have on your unit whether you may want to download any maps. You can get maps free from here: https://extract.bbbike.org/. Use the Latin1 Garmin maps. The UTF ones won’t work.
ClimbPro works anywhere. It uses the elevation data in the route file so maps are irrelevant for it.
GPX routes from Strava or other route planners don’t include navigation. The navigation prompts are generated by your Garmin by comparing the route in the route file to the installed maps.
ClimbPro will work without maps as long as you don’t have turn by turn navigation turned on as without maps your Garmin can’t create the navigation prompts so it will fail to follow the route. If you follow a route without using navigation it would work.
ClimbPro will only work if the route file has elevation data so whatever route planner you use will need to include that. The Strava route planner does as far as I know.
I’ve got the map, it was already on my Garmin, and have now got the route/course(s) on it, although it still has older local courses that aren’t Starred in Strava on the Garmin… I’ll try another few syncs.