I'm pretty sure OsmAnd renders all the roads, buildings etc on demand, which is why it's slow. It has to be able to rerender since it supports different styles, but it doesn't seem like it caches the results or prerenders adjacent tiles.
EDIT: performance issues seem to not be due to rendering the vector data[1].
EDIT: performance issues seem to not be due to rendering the vector data[1].
[1] https://github.com/osmandapp/OsmAnd/issues/8370