Game behavior on PC platforms vary due to hardware, game engine, OS tweaks, etc. I imagine with a PS5 you are stuck with a baseline behavior from the hardware and most behavior variations derive from the game engine and how it's implemented on a platform, in your case the PS5. The router is just a piece of the chain-link in a long line of variables that can effect the behavior of a game.
What have you done in order to reduce router buffer bloat? I'm currently using Traditional QoS and I'm finding it's the most consistent buffer bloat reducing implementation in a single-user home-networking case scenario. But at your speeds I don't think there's an option. Most buffer bloat options are for speeds of 300mbps and under UP/DOWN, AFAIK (correct me if I am wrong)