Hello JB - I've lived in Alaska for 50+ years and have driven the Alcan a few times. I own a 40' DP, a 26' Nash 26X TT and a 3/4T CC 4X4 diesel truck among other vehicles.
Before I retired about six years ago we went Stateside and bought the DP, left it in WA until spring when the ice was off of the Alcan and then brought it up. We used it one year here as planned to get familiar with it. Then I retired and we took a month to take it back down the Alcan. (When we came north in it from Vancouver, WA, we made in 99 hours from driveway to driveway.)
A 40' DP is too large for everyday use in Alaska if you really want to see things. If you already own one and coming up for a vacation, come on up in it though.
We base the DP usually in the El Mirage area west of Phoenix because of the plane connections on Alaska Airlines in and out of Phoenix. We have left it various other places in the States when we make longer trips.
After not having an RV for a couple of years up here, we decideded we needed something for summer use as we snowbird and go to the DP during the winter. Previuously we had a TC, enjoyed it, and got around well in it with just us and the dog - though he was a 200# Saint Bernard. We preferred to not have another TC so after a lot of looking we settled on a Nash 26X TT. A very nice, well made, solid unit, though it is on the heavy side.
To answer your first question, yes your 26' TT is fine with a few qualifications. Mine has 16" tires and the axles lowered so I have all sorts of ground clearance for pulling off of the side of the pavement or down some dirt roads. Hopefully you're not riding on 14" wheels. Having said that, you will still get around better and find more or better camping spots with a TT.
Either way, I'd upgrade to a 3/4T 4X4 truck. There probably aren't more than a half doze 2WD pick-up trucks in Alaska. Dealers don't even carry new ones on their sales lot.
Yes, you're pulling your 26' TT with your F150 now, but the Alcan and Alaska has a lot of mountains, steep grades, dirt roads, etc. With a 3/4T you'll get better brakes and a better transmission.
If you're happy with your current TT, I'd just upgrade to a 3/4T 4X4 truck. Gas or diesel, both will work. I'm prejudiced towards diesel. I haven't owned a gas rig since the late 80s(?) when Chevy came out with the 6.2 diesel except for my Jeeps.
Again, the 26' TT will work, but a TC will get you into more camping spaces. Do you prefer full hook ups, in which case space doesn't matter. Or if you want to camp by yourself Canada and Alaska has places all over to just pull off into if you've got a small rig.
Bill
Nodwell RN110 out moose hunting. 4-53 Detroit, Clark 5 spd, 40" wide tracks, 10:00x20 tires, 16,000# capacity, 22,000# weight. You know the mud is getting deep when it's coming in the doors.