All three systems/distributions are a based on Debian. DebEX KDE is based on Debian Jessie (Debian 8.6). DebEX LXQt and DebEX Gnome are based on Debian testing (Stretch) and Debian unstable (Sid).
As the name suggests, DebEX Barebone has only a minimum of software installed in advance. Among them LXTerminal, Thunar, Leafpad, AlsaPlayer, Wicd, Firefox, Thunderbird, Google Chrome, Tor Browser (in the LXQt version), GParted and Synaptic. In version 161007 and 161001 all common Gnome/Mate respectively KDE packages instead of LXQt.
DebEX uses Apt (apt-get) and Synaptic. I have also installed Pacapt ('an Arch's pacman-like package manager').