None at all, actually.
Such AiO (All-in-One) water cooling systems are supplied by the manufacturer completely ready for operation, including the liquid. Refilling is not necessary or, as a rule, not even possible.
Hi, I have mounted the Silentloop 240 on a Ryzen 5 2600x, i.e. Am4, and it runs really well, but please read the instructions carefully. I had difficulties putting it together myself, even though I was doing it for the 3rd time for a friend.
You can use liquid metal without any problems.
The Be quiet! product page states the following:
"Nickel-plated base plate allows the use of thermally conductive liquid metal paste".
Greetings
As far as I can tell from the manufacturer's site, this is only possible on the top or bottom for a 240mm radiator. I recommend mounting on the top.
Manufacturer's website: http://www.coolermaster.com/case/full-tower/trooper/
Anleitung: http://www.coolermaster.com/xresserver01-DLFILE-P15073000071670-F160129000688cd.html
Yes, it should work. Be quiet is very attentive. They have retrofitted every kit for the AM4 socket. Digitec probably just hasn't added this yet because, as I said, it was only added later. P.S. Which Ryzen CPU are you planning to buy? A normal air cooler is sufficient for most CPUs.