Hey, you can add the satellite imagery you need by doing Configure Map > Underlay > Underlay map > Add more. Then you can select the imagery you just added from that same menu.
After you've selected the underlay map, you can pre-download the images for offline use by viewing the part of the map you want to download, touching&holding anywhere on it, then doing Actions > Download Map.
Hope that helps.
OsmAnd does support this. You need to activate the overlay/underlay you want to download, press&hold anywhere on the map, then in the menu do Actions > Download Map.