I tried gaming over 3G a while back and it was fine for "slow games"like Eve Online or Civ where a bit of lag wasn't that important but for more "twitchy" games like FPS etc where reactions are important then even I noticed the latency, and I am rubbish at them.
From what I read, once the ping goes over 100 ms it actively impairs you performance vs low ping players in games which require "reactions"
I believe you can get down to 80 ms lag on 4G, no idea about 5G
C