Procedural terrain vegetation & curved UI (No Mans Sky)

hello :)

I am trying to recreate no mans sky, however, since it is my first project I'm leaving out the space part and just having a stationary spaceship sit on the ground.

I've watched some videos about terrain generation using noise maps, however, they do not have any grass ect. I know I can set colour to certain heights.

id like to randomly generate rocks amid constant coverage of grass, I know there is a way to stop the colour green from showing on steep surfaces but I am not too sure on how I could translate that into grass generation.

I would also like to implement a slightly curved UI similar to this image: