The RAM sits below the heat sink above the CPU socket. The rad and fans are going to contact that heat sink before the RAM. I have a gigabyte z370 gaming 7 and I used to have a gigabyte z170 gaming 7. The only issues I have ever had was the size of the heat sink at the top of the board.
I dont know what the Kraken would have a RAM height clearance. Typically it is best to go liquid because a big air cooler wont fit due to RAM or case clearance. Maybe the tubes on the pump extend out to the RAM, but I dont know what they are talking about. I looked at the spec sheet for the Kraken 52 and I did not see anything about RAM clearance.