In reply to ecrinscollective:
outdooractive.com is great, but you need to pay to get the Swiss Topo and official Italian maps. I think it's worth it though. The OSM maps are good but you can't beat Swiss Topo. Sadly you have to pay even more to get the Alpine Club maps, but for CH and Italy that's not an issue - for Austria and Germany you'd want those though. The official Italian maps aren't great, I prefer the OSM maps in that case, and I don't think outdooractive has the Tabacco maps which are the best Italian maps (for the Dolomites only though).
The Swiss Alpine Club site is superb, you can view Swiss Topo maps (with official route overlays) without paying but they don't have an app as far as I know, so not so useful on the phone. https://www.sac-cas.ch/en/huts-and-tours/sac-route-portal/ . If you subscribe (£3 per month) you can see route details, but the mapping is free. Would be an excellent tool for planning.