Don't own a new one, but have an old one and put in my share at SubaruOutback.org
The CVT or any Subaru Auto can't be engine off coasted. The center differential (clutch pack) relies on it running to keep it cool, and it will burn up in a very short time (My AT Warning light comes on after only a few feet.)
The manual is getting slightly better numbers because it can EOC while hypermiling. Here is a page showing what most people are reporting:
2010 Gas Mileage - Subaru Outback - Subaru Outback Forums
As far as tires, honestly you'll be fine with the stock tires as long as it's not 2 feet of snow on top of 3 feet of mud. My LRR tires have gotten me in plenty silly places.
