What are the coasters on the Nolimits 2 home screen?

Are they in the simulator? Rather ask than assume.

[Coasterkidmwm]

I'd assume no, but the blue one that snakes around the front I think perhaps appears in the Steam release trailer they made called "One Take".

https://www.youtube.com/watch?v=Wkli_A9v8sM

That is the best I can do to answer your question. Aside from that, the answer is "nowhere". Also the video was created after the game so the final blue ride may have been created to mimic the logo.

[TTD03]

I have wondered this as well.
We should ask the devs.

Wow! That's my first time seeing that video. I bet that's a real park you could "download". Those supports at the end had flags attached to them. I wonder how you do that in NL2.