Quick question: Does anyone have any information regarding whether all the different 64 bit release versions of Firefox floating out there also going to enforce the new add-on signature policy?
The signing process is independent of any platform, so the answer is yes.
Considering that these versions of Firefox might fall under the “unbranded builds” category, it is up to the maintainers discretion whether they are going to turn the feature on or off.
At least for Waterfox https://www.reddit.com/r/waterfox/comments/30l3zv/mozillas_new_addon_signing_process/ it was said that it might be turned off, but that was 4 months ago. I was hoping someone might have some newer information.
Unofficial builds are not supported by Mozilla. The official 64bit builds by Mozilla will behave in the same way as 32bit builds.