The bugfix branch is the “beta” version of the regular firmware, it is ahead of the current stable release, and bugfix 2 is the newer version that bugfix 1. Kinda. I only have a maintained bugfix 2 branch so it is the only option for you. All of the files other than bugfix 1 are bugfix version 2 with settings specific to each machine.
I have instructions on how to load the Beta on the firmware page. Unfortunately it is not that easy right now. Both arduino and Marlin are changing a lot right now.