Mesh with multiple texture

Hi all!

What would be the most efficient way to texture a "terrain" that is constructed from simple meshes or planes with the minimum amount of vertices? (Using URP)
If I were to use the Pro Builder to construct a level and wanted to draw different textures on the "ground", to use for example the PolyBrush, I should have a lot of vertex density (which I don't need, since the ground is always flat with possible stairs etc.), since the PolyBrush texture painting works with vertex painting.
Would a splat mapping technique work better here? (Using RGBA channels to define the placement of the different textures on meshes). Any good plugins? I can't find anything within Unity that helps me here.
The game is for mobile devices so it would be a huge waste of resources to use dense meshes for flat ground.

Best,
Niko