DS and DD2 each have a double Pax in their bedrooms, and in our bedroom we have custom built cupboards in the eaves, but built to Pax dimensions so we can use all the fittings (canny!).
So can't help with single vs double, or glass doors, but here's my input...
The tall version (if you have the ceiling height) is brilliant, and the top shelves swallow suitcases, spare linen and all sorts of things you don't need too often. You'll need a chair nearby!
Wire baskets are fine for clothes, and cheap, and give you more storage space than the wooden drawers. But they do sometimes fall off their runners if overloaded.
Get some of the square canvas pullout boxes for the base of the wardrobe - excellent for shoes and handbags.
I have a brilliant slide-out belt holder (with hooks along it) which I use for all my long necklaces. It hides neatly inside the wardrobe, next to the hanging rail.
Nothing is forever with Pax. The wardrobe in DD2's room used to be a computer cupboard, with a pull out desk and lots of shelves. It was dead easy to change all the interior and reuse it as a traditional wardrobe, and I'm sure it will evolve into something else at some point.