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
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.