Game manual got nothing about XCE. You can find every info about XCE and X-Division at
https://www.goldhawkinteractive.com/forums/. I can't explain tons of things already explained somewhere else.
Xenonauts systems are well as suppression, moral, covers and more. The problem is, you need to know exactly how they work. The key thing here, Xenonauts did not used tons of things it has at it's code. I mean there is damage types and resistances at the game code, but the default game did not use them. You can create many things with your imagination and right coding. There is very few information about tricky modding of this game and many codes are hidden/never used. I came late to xenonauts community when it was already late and many big modders left the game but after more then 1 year work and communication with XCE coders, my mod team and i know nearly anything about this game coding.
There is some unique things openxcom got, like different ammunition for same weapons. Sadly, xenonauts ammo code is beyond repair (or need a crazy dedicated coder).
But there are things that openxcom never have like a great, complicated and tactical airgame and A HD graphical approach with X-Com atmosphere. Xenonauts can have much more maybe but sadly we are very few people left. If we had people, as you have here, Xenonauts could be a new X-Com.. but the beginning did not take enough attention.
Xenonauts made a new generation X-Com clone but with limited power on a bad engine so i think it deserve the respect as same as openxcom. Even the story of the development of the xenonauts is a very sad one with many drawbacks in it. Now they are doing the 2. game with much dedicated and pro vision. But as X-Division mod team, we want this mod as a new game. If you check the additions and image/videos, you will see something totally different. Maybe even we can find some people here wanna help us too.. because this community is the best xcom modders..