The realistic density mod is one of the most game changing and I wouldn’t recommend it until you’re very familiar with the game and how it works/models.

Biffa has some good videos on traffic solving: https://m.youtube.com/channel/UCYzO4HZxgXc2UJQD5bIo8AQ

It works somewhat realistically but you have to learn the limitations of the simulator if you want mass transit besides busses used well.