The AC file object density isn't anywhere near as bad Manhattan which happens to be almost all AC file buildings (and seemingly more buidlings than needed) - so CPU bound FPS hit isn't bad. Manhattan is probably the worst case by far because of the cutofff point between AC file and shader buildings - areas around even other big city centers seem to have a mixture of the building types, while Manhattan is all AC file buildings.
However, people with even old pre-Ryzen AMD processors were getting 12-15 FPS in Manhattan [
1] - not to mention Manhattan reportedly working (i.e.benefiting visuals) with LoDs turned down on a 4GB 2 core laptop with a mobile GPU.
The city textures would have looked a bit better with photoscenery in that screenshot, but it's a tradeoff - the area around Madrid has updated regional definitions with increased detail which isn't visible as the surrounding terrain was covered by haze/fog. The solution to the city textures problem is texture switching once objects have loaded.
I think the reason you may be getting low FPS is because you're running many (high resolution?) monitors from one GPU - or/and maybe that GPU is also bottlenecking in the rasterisation stage with settings AA turned up .
Kind regards