I vote no greenboard. Just CB, half-inch. With proper framing it's a great stand alone backer for tile.
You need a vapor barrier between the CB and the insulation. Water can migrate through the grout/tile. It's likely that it won't but it can. Once through, it can migrate through the cb and into your insulation.
Around here (CT), the norm is unfaced insulation...either FG batts or cellulose. The exterior walls with batts get a 6-mil poly vapor barrier.
Walls that will be tiled then get horizontally run tar paper stapled to the studs, overlaped to shed water. It's by no means vapor-tight...it's just another skin to shed water.
Then cement board. I use Wonderboard on bath walls that will be tiled.