The switch enabled improved anti-aliasing (SMAA) and better long-range Level of Detail (LOD).
1.36 breaks many 1.35 mods, especially:
Set "Shadow Texture Size" to instead of Ultra. The DX11 shadows are 4x more demanding than DX9. "High" still offers crisp edges but uses 70% less VRAM. ets2 135 to 136 patch top