In Fortnite,i get stutterings while gaming and the lobby. Also when I'm joining a match it loads slower than my previous rx570. In games like GTA and cs:go I have low fps. I don't know if the problem is the RAM the 5700 XT or the drivers.
I have pretty much the same set up and I experience the exact same issues, stuttering in the lobby in Fortnite and most of the time low fps in GTA. So I don't think it's your ram. If you find something, please let me know! I might try the newest drivers, I am currently using the previous version. I'll update if it works.