Yes, I'm afraid we can't do much to speed this up. You can argue that this problem only happens with A7 and you're possibly right, but this does not help - we can't fix it here because we are not connected to nVidia and don't have the source of the code where this happens.

The problem is probably unrelated to the 8800, it happens with the driver version 169 and is caused by rendering 3D and 2D together - I can tell this much. That's why you have it with postprocessing, which is 2d rendering, and why it happens more frequently when you have particles active, which are also rendered in 2D. You can try to improve the behavior by switching to 3D particles - for this set the experimental particle_mode variable at 1.