That is beautiful and oooohhh lots of quilting opportunities!! I'm going to approach this from a hand quilting perspective because that is what i do....
I'd shadow quilt around the squares and triangles. Or you could shadow quilt around the triangles and make an X thru the 4patch squares.
I'd find a border stencil to use in the white areas/sashing.
The rest of the borders could be done in a cross-hatching or a combination of other border stencils.
I realize that you are wanting to machine quilt this, but maybe this can give you some ideas.