The portable builds are fully portable, the profile directory is inside the browser folder. It does not touch appdata at all.
Also if you want a classic Chrome/Chromium like theme better than the default, try Geckium.
Notable bugs:
The 32 bit build is built with --disable-sandbox. With the sandbox enabled under Vista, the browser fails to open multiple processes which breaks the browser. The 64 bit build is fine. Considering Mypal68 globally disables the sandbox, I don't think it's that bad. If this really is a big issue then please pr a fix.
Changes on top of the previous 131.0.3 build:
Added the ability to enable/disable the r3dfox theme's drag space.
Haven't tested on XP (OCAPI) nor have I extensively stability tested.
Please let me know what bugs or issues you encounter with it.