I use a combination of paper maps and an overview map on paper. For trails like Annapurna circuit or Everest Base Camp, the paper leaflets are quite helpful as they help you plan the hike by days. However, I prefer the digital maps, specially OSM because the sheer amount of information they contain, and I can contribute too. Not every shelter has running water, hot water, electricity, etc. Not many maps indicate them either. But OSM is full of these small yet helpful information.
On an iphone, I can't recommend https://mapout.app/ enough. It's simple & good-looking, it's easy to download tiles of the area you need (not countries) while on wifi, but designed to work mostly offline. It's a few dollars up front & then zero nagging.
Friend on Android like OsmAnd, which sounds like a much bigger app, contours are an add-on IIRC. I think can even do things like editing the map & submitting your corrections.
I have never got around to printing maps, but have occasionally carried paper maps too. OSM is not as detailed as the best EU country maps, but is far better than anything on paper in most faraway mountain ranges.
I use maps.me, and there are several user-contributed walking trails.
For unmarked trails, I draw a few trails using Google Earth Pro, and export it to maps.me, which will then draw the waypoints and trail on the map. There are communities like GPSies that share similar trails as downloadable KML files.
I use an Android phone with 6" screen + 5,000 mAh battery, accompanied with a 20,000 mAh power bank. With music playback for 7-8 hours, and occasional maps use, it's good enough to last 5-6 days in airplane mode.
