So after trying what I layed out above, but without success I ended up with setting up the new drive from scratch then restore some partitions from Acronis/TrueImage backups. Still not quite there, but my main Windows system is up and running, the second Windows and Linux Mint are in their raw bootable states. Probably the best way to do this.
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meanwhile I solved this differently: installed 2x Win10 on the new main hard drive then installed Linux on my now free old 250GB SSD and put it into an external USB 3enclosure- Not quite as fast as it would be if I could boot from an internal drive but still fast enough for me. Everything else I tried somehow didn't work