Let's tackle those frame drops you're seeing when looking at the city lights first! The main thing to understand is that all those nighttime effects can really push your hardware to its limits, but there's definitely ways to smooth things out.

Starting with the basics youll want to turn down those shadow settings since they tend to pile up when there's lots of light sources around the city, and dropping water quality down to normal usually helps a ton especially if you're running amd hardware. Something interesting to keep in mind is that the engine gets a bit overwhelmed when it's trying to handle all those streetlights reflections and building details at once, so don't feel bad about tweaking things down a bit

for the more technical side of things you might want to try capping your frames just below your monitor's refresh rate using something like afterburner, and switching to adaptive sync through your graphics card settings instead of using the in game vsync can make everything feel smoother. If you're running a ryzen setup, your ram speed might actually be holding you back a bit when loading all those city assets

good to know for you the game engine is actually pretty old school when it comes to handling multiple light sources at night so you'll probably need to find a sweet spot between visual quality and performance. Usually dropping msaa and playing with shadow settings gives you the best balance without making the game look too rough