Below there is my table for zooms and scales:
"Zoom level (m, km)" - no comment it is zoom from device screen.
"Lower visible JNX scale value" - it is general issue
"Alex" - it is recommendation of author (if empty so this is intermediate and neutral zoom on device which is not depended of scale of JNX and it is the same as corresponding high level)

Spoiler: My table
"Zoom level (m, km)" "Lower visible JNX scale value" "Alex"
5m 14
8m 21
12m 32
20m 52 75
30m 79
50m 131 149
80m 209 298
120m 313
200m 521 597
300m 782 1194
500m 1303
800m 2084 2388
1.2km 3125 4777
2km 5209
3km 7813 9554
5km 13021 19109
8km 20834
12km 31250 38218
20km 52084 76437
30km 78125
50km 130209 152877
80km 208334 305758
120km 312500
200km 520834 611526
300km 781250 1223072
500km 1302084
800km 2083334 2446184
1200km - 4891969


P.S. I think you can to determine borders of the actual image in MAPC2MAPC with input data for project - it will be equal cropping in export in JNX.