Just checked out what PPdS involves – do not get a Big Hit!!
It can be ridden up mountains, I have done so, but its a hell of an effort. They were Welsh mountains & I reckon climbing in the Alps on one would be a nightmare :)
I’d be looking for a Rocky Mountain Slayer (pref SXC), 05/06 Spesh Enduro or similar 6″ travel bike for something like this that is ok to climb on & great for descending. SX Trail could be ok, but would be a little harder than an Enduro to climb on.
Re: size. Hard to say. I know a guide who’s 6’2″ & rides medium bikes, but he’s pretty skinny, if you’re wide as well as tall a large could be more suitable.
I’m 5’8″ and have a mix of small and medium bikes. For me medium = a bit big but very stable and small = very chuckable/easy to jump.