By deleting the saved session in xfce4-session-settings and making sure to not save current session in the shutdown menu, Enpass now starts minimized to tray as it should.
Since session saving is not a must for me (the only need I have for it is having two instances of conky running on startup, and I can achieve the same thing with scripts) this has effectively solved the issue for me.
[Manjaro] Can't start in tray
in Linux
Posted
Worked in Arch with XFCE 4.14