16Gb minimum.
For me, gone are 2x4Gb..8Gb definitely not enough when you consider Windows alone with normal everyday apps installed, will consume almost(if not more than) 2Gb of those 8Gb, so you're left with 6Gb for gaming.
Anything above 1080p in latest titles may struggle in CPU/GPU intensive scenes.
I remember when RAM prices where crazy through the roof, had just gotten my Ryzen 1600 system and only had 1 stick of 8Gb of RAM, playing PUGB with 8Gb of RAM (single channel...obviously)..everything was fine...looting..driving...but the moment I met other players in game, and a gunfight ensued, insta-frame-drops...making it unplayable (since the whole point is to survive during a gunfight).
Waited another month then bit the bullet on a 2nd stick of 8Gb for £70-£80.
Never am I going lower than 16Gb of RAM for my gaming rig, ever again ( only if it's for my HTPC..then 8Gb is plenty).