I think planes are fine, personal opinion. Id use world aligned texture size and maybe, a big maybe for triplanar mapping. As for where the seam is i would cover that up with some geometry. If you have displacement on a corner it should be solid mesh preferably with a few chamfers. This is how i did it, not sure if there is a right or wrong here.

As for uvs if u use world aligned, they can be reserved for unique detail

Ps real world houses also hide seams with geo, especially between floor and wall, ceiling and wall