Did u modify registry to get old right click context menu back? I had similar problem after using online guide to modify registry to get old context menu back for sake of convenience . However it seems to destabilize new taskbar so I had to undo the registry and everything back to normal. Guess I had to wait for developer like 7zip and notepad++ to add support to new context menu like winrar and nanazip.

After upgrade my firefox run fine ;can't comment about opera since I do not use it. My advise will be try backup ur browser setting and then reinstall them on win 11.

Another noticeable minor bug  for taskbar is when u hover over it will not display battery estimated remaining time but it was found in settings. Furthermore, when u hover over to blank space taskbar it will show some popup like speaker or volume if hover to those icons before.

You can download the iso from Microsoft, then just double click on it, then just run the setup exe

You'll have an option to keep all your data