For instance in this area zoom 14 for the black box is 400 MB which my device can handle, and had plenty of detail for overview and context. However hiking and so on will be better served by zoom 15 or 16, but I 'd only need that for a kilometre or two alongside the track.
https://imgur.com/gallery/6z1M4jQ
Black box would be level 14, yellow 15 or 16.