Green Pass Questions

Ordered a 14-day Green Pass for our upcoming ski trip to Niseko. Traveling from Sapporo to Niseko and then winding out way south to end up leaving from Tokyo, and I just had a couple of questions I couldn't find exact answers to.
1 - I know that Green Cars require reservations, but can the green pass be used just like a regular pass if you aren't using or there is no green car?

2 - Some people have said that they bought a green pass because they are traveling with more luggage. Do the green cars actually have significantly more luggage space? We won't have a bunch of luggage but the bags we do have will probably be large (have to bring our ski boots, jackets, helmets, etc), should we anticipate this being a problem?

3 - Will JR Pass work on the bus shuttles from Kutchan station to Hirafu village or are those private entities? Will luggage be a problem on those, or is a taxi better?