I think i know the main problem with the Lag, Stutter and FPS issues with the game.
If you notice when you die the players in the game actually disappear. That being said watch your FPS sky rocket as a result of all the players in the game disappear. Everything in the game stays Buildings, Loot, Dead players loot, Vehicles, Ect. The only thing missing is the players that are still alive. If you were playing Duo or Squad and go to spectate after you die your FPS drops way back down.
25 - 55 FPS when Alive
80 - 100 FPS when they disappear when i die.