Hi Aidan
I suspect that this posting would better be placed in the Basics section, facilitating more replies.
If these are 2 separate files (different names and resources saved using their unique names), I'm not sure why they wouldn't each open their designated resource folder. But, then again, I haven't tried this as I will usually save each .imp, even a variation of the same pub with the same name, in a separate folder. Not very economic, but seems to avoid confusion, and possibly the issue you are experiencing.
Why not copy and paste the second .imp and its resource folder into a new folder? You will still be able to open both in Opus.
Now, as to cutting and pasting between the two .imp files: (1) assure that any variables, needed to support actions/script on any pages copied in, are copied into their destination .imp file variable tab. (2) I've experienced some difficulties cutting/pasting pages between pubs (.imp files) as have others reporting this on the Forum:
(
http://www.digitalgrapevine.info/viewtopic.php?t=1647&highlight=duplicate)
Some remedies, should duplication of objects occur, may be found in the postings as well. On the other hand, hopefully this may not occur.
Finally, to facilitate responses, you may want to move these questions over to the Basics section.
Hope this helps.
Kind Regards,