Has to be organic maps.
I was a big supporter of OSM+ but its just too buggy to be reliable - My last trip it constantly said "keep left" when driving ( a topography bug apparently) And it has got the wrong route too many times.
Unfortunately organic maps relies on your phones TTS for voice navigation - and I can't seem to get that working with grapheneOS (even third party TTS)
So this sent me down a rabbithole.
I can't answer about exporting data but having just done some research the 2 best options I have found for a privacy focused solution (open source) are either:
Bangle JS https://banglejs.com/
PineTime https://www.pine64.org/pinetime/
For me the bangle seems superior - I'm tempted to get one!