Some use ViewRanger but I prefer to stick to one system. I use an Ordnance Survey map on the fells when I walk so I use the Ordnance Survey App to plan my routes.
I use Ordnance Survey Premium which means I can plot my routes on the PC. The app works out some stats for me and I can save the route for use later, even on the fells.
I like to add some icons on Photoshop before posting on the Walking The Wainwrights group. For me it’s worth it just for this and being able to view any OS map online.
You also get access to all maps and the ability to plot routes on OS maps on your phone. If you want to download maps to your phone for when you have no signal you can do this with the subscription.
When you plot a route the app works out the distance, ascent and time (you choose you’re walking speed).
I haven’t gotten on with ViewRanger in the past so I tried this, better I think, especially as you have to buy maps on ViewRanger (£35 I think for the Lakes, 4 OS maps, may have changed).
At the end of the day a map is invaluable so trying it out for twenty quid, trying ViewRanger, buying a map… Do what you need to do to make sure your navigation works for you.
Batteries run out of course, especially if you’re new to navigating and have the phone on a lot. I wouldn’t recommend you go very far without learning to navigate properly using a paper map and a compass. Being a Mountain Leader I am qualified to teach you how to navigate and read a map, how to plot a route and what to take into consideration, even night navigation..