I have talked a bit about their design in their support forums, so I will mainly be repeating some things from there.
An EK rep can feel free to quote me to fix whatever mistakes I make, but here goes.
You are buying an AIO unit, its not really meant to be dismantled. The fittings are on super tight, you either need some butter or other lubricants to open them, I used a rubber surface so that any sweat on my fingers didn't cause me to loose grip. Then I twisted one off.
I bought plenty of tubing, but with only 1m you should have enough to make a simple loop with the rad mounted in the top of the case.
The drain plug opens with an 6mm? Allen key. It doesn't follow with the unit because its a fairly common tool and refilling the unit is not necesarry. An AIO, remember? The screws for the fans also use a different bit. It is a torx type, can't remember the size. The key is for dismanteling the backplate on some motherboards, otherwise it couldn't be mounted universally.
The QDC plug seemed hard to remove for me as well, I just let it stay on just so that I can swap back if I want to sell the complete unit for some reason.
The fittings are REALLY tight though. I couldn't see glue on mine I think, but who knows. I got one off with a bit of work and the knowledge that if I messed it up, I still had more cable to make a new loop. If I was scared of breaking it, I probably wouldn't have gotten it loose tbh.