Tile game instatiation

Depends on the size of the map, if you use a mesh to render your tiles it should be relatively okay to render the entire map if it doesn't exceed the mesh's maximum vertices. If however you a have a gameobject for every tile (which is not recommended) it is best to not render everything at once, and use loading screens to instantiate parts of the map when the user comes in range and possibly objectpool it so that revisiting those parts of the map can load a lot faster.