The Anti-pop up setting. Before, it controlled only things being drawn by the Addon Manager but, since our most recent sceneries draw objects almost exclusively using Couatl, the setting because less and less useful.
Now, it controls both the Addon Manager and the Couatl objects with a single slider, so you should see its impact very easily.
Increase it, and get better smoothness, less fps and more risk of OOMs, just like any other scenery out there running under a 32 bit sim.
Decrease it, and get better fps, way less risk of OOM-ing, and likely more stutters.
Note that, this doesn't have any effect on GSX itself (which has its entirely separate memory management method, related to your selected parkings), but only the sceneries.