Librewolf portable [0] is available via the PortableApps.com launcher, which is great for keeping it from scattering files everywhere or for carrying it on a USB drive for Win32/Wine users. Waterfox Classic used to be available, but that stopped a long time ago, and the new Waterfox was never available, to my knowledge. Additionally, the portable version of Librewolf, while lagging slightly as most portable editions do, is updated fairly frequently.
This is why I ended up choosing Librewolf - I prefer to have more control over where files are stored on the Windows platform. I also took the extra step of creating the TempForPortableApps [1] folder as well.
That's a great shout. Portable versions of apps are really useful if you want to sync tools e.g. over syncthing/pCloud/Dropbox, or you work for companies with draconian installation policies.
This is why I ended up choosing Librewolf - I prefer to have more control over where files are stored on the Windows platform. I also took the extra step of creating the TempForPortableApps [1] folder as well.
[0] https://portableapps.com/apps/internet/librewolf-portable
[1] https://portableapps.com/support/platform#advanced