I've got a high end machine (i9, Titan XP, 64Gb RAM, Ubuntu 18.04) and PZ flows as smooth as butter for the most part but I'm having a repeated problem where the game will suffer micro stutters if I drive out of a cell where I have built structures and return back into it.
For example my safe house is in the single story farmhosue north of Rosewood (the one with the fenced back yard). I can play for hours there with no issues. Say I drive to the farmer's market south of Rosewood near the army camp or to the Muldraugh crossroads gameplay remains smooth. But then I return and when I near the safe house the client starts micro pausing until I exit to main menu and continue. No errors in the console, or unexpected spikes in CPU/GPU utilization