The VNC solutions connecting between mac and windows don't seem to be much good when it comes to the clipboard. I don't know what client you used on MAC to connect to Windows TightVNC server. I tried chicken of the VNC,(mac to windows) and found the clipboard sharing to be poor e.g. seamless one way and not the other way. And I tried TightVNC(windows to MAC - mac's native remote desktop server allows tightvnc client/viewer to connect to it) and found clipboard sharing not happening in the sense of working both ways.
There is an app developed by Microsoft for MAC, which is a remote desktop client for Mac. So that can let you connect Mac to Windows. I haven't used it much but as far as I can tell you get proper clipboard sharing with that. You can find it in the app store. Microsoft remote desktop 10. https://apps.apple.com/gb/app/microsoft-remote-desktop-10/id1295203466?mt=12 i'm connecting fine Mac to a Windows 7 machine with that.
Like with the windows remote desktop client, the windows server you connect to will log out(which I don't like, it's a bit invasive). So i'm currently going Mac (With MS remote desktop) to a Windows computer I don't mind automatically logging out from, and running TightVNC viewer from there, to a windows computer running TightVNC server.
Prior to MS remote desktop, people used 'cord' on mac, which was a remote desktop client for mac, but now MS have written one and it works better. And Cord is now deprecated, has a bug where it crashes when a window is moved(which they fixed in code but have not bothered to fix in release), and it's no longer being developed.