I made a gravel bike from parts. It had 10sp Campagnolo Chorus crank and a Shimano/Microshift drivetrain. The chainline was a wee bit medial of where it should be. The native Campy bearings weren't sealed and were rather old at this point. I used this as an excuse to get one of those super shiny IRD bottom brackets. If I recall, I got one one about 4mm shorter than I would have needed in ISO. It worked perfectly

It was 1x, so it didn't need to shift. Once it was dialed though, no chain drops. That part took some time though.

I don't know if that answers your question. Yes they're close enough to fit together. They don't randomly loosen. Nothing exploded. Just gotta account for the difference in where it would tighten to.

I do wonder if a JSO BB would deform an ISO crank, so that once you made the swap you can never go back. I don't know, I didn't try.