I am not a fan because they install all that WINE stuff on the system level which is a huge security degradation.
I disagree with this. Sure, it could be made more secure, but Wine, on it’s own isn’t, any greater security risk compared to any other scripting runtime such as say Python, which is also installed at the system level. Ultimately it’s up to the user to get their executables from trustworthy sources - and whether it’s a random bash script or an exe, doesn’t really make a difference.
As for Firefox, if you’re truly concerned about security then you wouldn’t be using it in the first place, you’d be using Librewolf, which you can install without any issues.