escorted tours is more like they do at Tauck and Globus, where someone stays with you the whole time and is your own tour guide. Happens a lot in canadian Rockies. Not necessary here, a land tour would be fine.
We just got back and did land tour first. I recommend that since it is fairly tiring with all the moving and packing and unpacking. You also get up fairly early on each day to do Denali and other tours (Denali buses start leaving at around 5:45 a.m.)
Finally, the other reason I would recommend southbound is that at the end of the trip, you will only have to travel back from Vancouver, as opposed to Alaska, which adds at least another 5-7 hours of travel time. Hope this was helpful