I use routes created with RWGPS directly in RWGPS on my phone in airplane mode...not sure why I would need to load it to maps.me

Having said that - I also use Mapy.cz app which allows you to download entire countries and use the maps off line.
in some cases mapy.cz has better bike infrastructure markings. For example during my Scotland trip the EV Route numbers and dotted lines accompanied the downloaded map and could be directly zoomed into for inspection to make sure I'm on the trail or off