So it was only the 32-bit executable that was affected?

By default CCleaner installs both the 32-bit and 64-bit versions, however on 64-bit systems it only runs the 64-bit executable and points every shortcut it makes to the 64-bit executable.

On one of my affected systems that appears to have had 5.33 installed, I noticed no registry keys that appear to be created and that system never ran the 32-bit executable.

Would it be safe to assume it's not affected and simply uninstalling CCleaner 5.33 is enough?

Piriform seems to suggest that only some useless system information was ever released by the compromised version. The general worry is that it wasn't just that information, but also other more important things like account logins and such.