They are not only capable, but are also very robust. My personal preference is for OrganicMaps because of its nice UI and extensive maps (thanks to the OpenStreetMaps project!). Another app implementing the OSM project is called OSMAnd (the and standing for android). It is pretty good as well, though I do prefer the first app since you can install it through the much more secure GoS (grapheneos) provided Accrescent appstore.
Thank you for deciding to switch to GrapheneOS and I hope you have a smooth journey.