1. Find heavy forest area (Tested on Livonia and Tanoa)
2. Set objects quality to Standard or above
3. Set shadow distance to any large number (500m, 1km or above)

Now GPU utilization is low which results also in very low FPS

Tests on Linovia, everything is high:
3km shadows - low FPS and GPU utilization

1.5km - same FPS as 3km (despite a 50% reduction in range)

500m - still low FPS (better then above, but GPU is underutilized)

5m - normal FPS (also normal GPU utilization with stable 60 fps cap)

Return 3km shadows, but set them to the worst quality - same FPS as on the best quality (despite a huge difference in shadow map resolution and filtering)

Leave shadow distance at 3km, but disable them - low FPS and GPU utilization (while shadows completely removed!)

Set objects quality to the worst quality - normal FPS and GPU utilization (while shadows still 3km!)

Move to big town - instantly x2 FPS

Move to Kavala on Altis (no forest, but still complex scene) - +50% to previos example, or x3 compare to forest on Livonia

Same in any urban area on any other map, also responds much better to changes in shadow quality and any other setting (but still not hight FPS if shadows disabled and shadow distance is high)