The newer iterations of the Unreal engine can do some phenomenal post processing.
Having said that, if you can run Cities Skylines smoothly with a big city, you ought to be on the right path.
I believe Paralives (Sims 5's main competitor) is built using the Unity engine (?not 100% sure though) which is the engine running Cities Skylines, as well as quite a few other games. The orthagonal building model they use was inspired by the way you lay streets in Cities Skylines if I recall correctly. The reason I mention this is because it seemed to me that they (Maxis / EA) were showing off things that were very similar to the Paralives video released earlier in the year. Competition between the two franchises is teriffic, because we (consumers) should get two great games rather than having one rest on its laurels and occasionally spit out a bit of DLC.