I use OsmAnd myself, and my main recommendation for folks is to use Gaia because it's... easier and less nerd knobby. But where OSM falls short is in tagging of mountain bike trails. Missing tags, no visualizers for contextual data like difficulty or route coloring on trail. Not to mention directionality on one-way trails, recommended (but not required) directions, the desire for showing routes on non-loop systems... etc.

Personally when navigating I use a combination of OsmAnd, TrailForks (carefully), and some sort of copy of the trail system's print map. This usually does me well.

I'm also working on a structure like this, which I hope to eventually use as an easy way to take OSM MTB trail data and present it on a slippy map, but it's still very much a casual side project / WIP: https://trailmaps.app/ramba