Track building works just fine. My grief is that it snaps to straight bit too easy, but it’s nothing one can’t handle.
Gradients are just as steep as you make them. If you want steeper, build shorter sections or manually control the slope.
103 is not bugged, it does go 200km/h but only with coaches able to go 200km/h. If you are restricted to 75mp/h then the limitation is coming from the coaches it’s pulling.