Terrain

Hello!
I am gathering information for building a mobile game . It is a little project that me and my friend would like to try and start . I have one question tho .
I would like to create a terrain similar to this -- >

I however heard somewhere in the forums (read) that terrain is not working or not proper for mobile games . It would be best to actually create it and import it to unity (from blender for example) .
My question to the community is , would you be able to give me some insight on where can I read or watch videos about good terrain generation . By good I mean good looking and optimized .
Would you be able to refer a book to me or a video that you have watched or a course . I really just want to learn to create a good looking terrain . Optimizing would also be very good topic to learn . I know that there are some tricks there as well.
Please post your references , guides or / and courses below .
Thank you , community and have a great Day/Night !

 

For optimising check out this cool article.
It might be a bit outdated, but the info given is still useful.

https://paladinstudios.com/2012/07/30/4-ways-to-increase-performance-of-your-unity-game/

 

Thank you !