Yeah it is pretty weird. Some people are having some servere FPS problems due the new update. Just make sure you got all your drivers updated and maybe that will help.
I think passengers would maybe inscrease the fun factor but they will be way to hard to realize. It will take alot of time since they can't just sit still. I mean you've prolly never seen a rollercoaster with 24 the same people on it not moving while in the ride. They would look really dumb because in real life the wind would make their clothes and hair wave but all that kinda stuff would slow the sim down way too much. Conclusion: impossible.