Huge Open world terrain setting HELP NEEDED!!!

Hello There, I’m starting making an huge open world map game (like minecraft but with better graphics)
My size for the terrain is going to be
5000 W
5000 L

Could any of you tell me what are the best settings for my terrain before i start (making the map)
Is it gonna be lag because of its size. or is there a way to make my character load just what he sees (oculus culling with terrain)

do i need to change detail distance because of the size of the map? or detail density? and how much?

What do i need to think about before i begin?

any tips.

Kind Regards.

Are you going to be editing the terrain inside the game?
If yes, then unity terrain is not really good solution for that…