It struck me that if some kind of subspace "wrinkle" could occur and copy a ship, what if an even larger wrinkle were have a star sytem pass through it?

The Voyager copy existed in practically the same space (perhaps offset slightly "out of our space time continuum", or perhaps more likely each being partially pushed into different subspace layers.

What if this was a wrinkle, but there were also "folds", with greater curvature - like a nasty fold you get in your best T-shirt when you're desperately trying to iron it flat. Such a fold might create a copy, but PUSH IT OUT OF THE SAME POSITION. A copy may be submerged in subspace, and so invisible to it's counterpart, but maybe this could wear off and after the copy has travelled a significant distance it re-enters normal space.

If so, what if the whole solar system had passed through such a fold? At say... 1960 AD? Wouldn't that start to explain the copy Earth in TOS: "miri"?

For that matter, what if it also could account for every parallel world that TOS showed but was a bit unlikely; The Roman world of "Bread and Circuses"?
The Yangs and Cooms of "Omega Glory"?
I know the continents were seen to be different on these worlds, but one could hand wave and speculate polar caps melting and geological upheavals over the time since their replication.

Just a crazy thought, but it sure helps me accept "Miri" as more feasible.

Good thinking, but they'd all have to have been created at the same time, and then been moved to wherever they ended up, which could only be explained by a huge, multi-mouthed wormhole opening and swallowing all the duplicates and moving them to different locations. I think it was just a joke Q was playing on us, personally. Seems a lot simpler.