I played cities on many configs from release and tried many mods, so on my opinion for playing with default mode pack with: Rico, 81 tiles, 700-1000+ assets from workshop, and placing many Props manually you must have as minimum:
Necessary SSD drive (do not try on hdd), and PCI-M2 ssd is much better.
4/8 core/thread cpu, better 6/12
16gig of ram as minimum, better 32
Gpu really not affects, starting from 1050ti, 1060, because now on rtx 2060 I have the same 20-30fps on mid setting