Enclosing a breezeway between house and garage, (there is an existing roof )

I am in Calif. I would like to enclose my breezeway. At front of house would be solid, possibly a transom window at top. At back yard side of breezeway, a set of French doors with a vinyl window at each side. I can’t find anybody to do it for me, so I think I should try it myself.

Although the front of house is lapboard, Iwould like this wall to be stuccoed. Would like to use cement board rather than plywood. Wondering how far back I should place the bottom plate to accommodate thickness of finish materials. Also, since bottom plate will be placed on existing concrete slab, I’d like to use a well recommended caulking under it so water will not creep in.