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?
While not scriptable and not super advanced, Windows 10 and Windows 11 have a native visual clipboard manager with history and some other basic features. And it works quite well.
Try pressing Win+V, and the OS will give you a prompt to enable clipboard manager in settings. Once you enabled it (has to be done once), next time you press Win+V, a panel will slide out from the right side, and you can see the last N entries in your clipboard (which could include text, images, etc.). You can pick anything from there and paste it, and you can also pin any item there so that it won’t be overwritten when the clipboard reaches the limit and starts writing over.
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?