Where there's ony 1 tag, either a v1 or a v2, I want to leave the file alone. It's only if both are present that I want to strip out the v1. I don't really want to re-process all the v1 files to make them v2.
Also, that tip doesn't "sync" the tags. I transfers from one to another. So, if I have both v1 and v2, it looks like I have to decide up-front which I want to populate the v2 with. Either the v1 or the v2.
You could right click the ListView columns (Filename, Path...) and select Customize columns .... Then add the TAG field from the left pane to the right one. If you want to apply changes only to files containing one tag, sort the list by clicking on the newly added TAG column and select the files which don't appear as having two tags.
Not exactly sure what you mean. If you want to copy the ID3v1 tags to the ID3v2 tags, select reading of ID3v1 and writing of ID3v2, select the files you want to edit, press [CTRL+C] and then [CTRL+V]. If you want to copy ID3v2 tags to ID3v1, select reading of ID3v2 tags and writing of ID3v1 tags.