They are meant as full installers for install on firmware 4.25 or greater, but they really only change a few files compared to what Mel-kior changed, mainly
/etc/init.d/rcS,
/adds/kbmenu/onstart/ksmhome.sh,
/usr/local/Kobo/udev/usb, and the QT drivers listed in
/adds/kbmenu/Qt/plugins and
/mnt/onboard/.adds/kbmenu_user/copyrepos/. It may reset settings to alternate booting between KSM and nickel as a safety feature (so you can still access things under nickel if things don't work) but you change it back to 'always' boot KSM by editing
.adds/kbmenu_user/runsettings.txt.
Yes to unzipping and placing the .tgz file into
.kobo. You can manage it the same way as any Kobo firmware upgrade, but if you're using KSM to install it, you'll probably want to use the full upgrade option.
But again, don't flash unless you have a way to revert. They both should work, but aren't heavily tested, especially the 4.33 version. But do chime in if they work or not so others can know too (especially with things like touch).