For Windows, there is "ClipboardFusion" by Binary Fortress, which acts as a scriptable clipboard manager, and could tick most of your boxes.

I'm not sure how possible it would be on Windows for a third party app to perform isolation - maybe if it registers a hook for when clipboard content changes which is somehow guaranteed to run first before other applications and any hooks they may have, it could swallow the event and clear the clipboard so other processes can't see it, and then do something similar with paste events maybe?