Thank you for the contribution! Unfortunately, London and Paris are by far the worst photogrammetry cities when it comes to shape retention at lower LOD levels, which is why they exhibit more morphing than the others. Basically, they look quite nice at higher LOD levels, but you will need to push Terrain LOD beyond 300 so that you can force them to render, and this cleans them up quite a bit.
Jörg has said in an interview that they plan to redo London at some point, which should improve its appearance. It is unknown whether Paris will receive the same treatment though.
Check at different fan speeds to make sure that it’s not an issue with the fans. Otherwise, it sounds like coil whine, which is fairly common and not harmful. Potential ways to fix it are capping your framerate to prevent the GPU from being maxed out, reducing any overclock, and undervolting it.