16 days probably isn't enough time to do a lazy sightseeing tour of BC and the Yukon, make a side trip to Haines AK, on your way to Alaska to have a look around. Problem is, the roads in northern BC and the Yukon can be pretty bad, they definitely aren't interstates, 55mph is the speed limit average up there for a reason. In places, it's too fast.
If you just head straight up through central BC to Prince George, you can decide which route you want to take to Watson Lake, YT. I've done the Alaska Hwy (Hwy 97), but not the Cassiar (Hwy 37) which is the other route. The Alaska Hwy has plenty of scenery and wildlife, as do the main highways in Alaska.
No idea what the Haines Hwy is like.
Sorry, not trying to rain on your parade, but 16 days to Alaska and back will be a challenging whirlwind tour. That said, it's doable, but I don't think you'll have a lot of time for stopping and sightseeing.
Try doing some google maps "routes" - I did Sacramento to Anchorage, it's around 3,000 miles one way and the average drive time is 60 hours. That's 6 X 10 hour drive days.
If you want to do the BC/Alberta border route north to see Banff/Jasper etc. it's 3400 miles one way.
Hope your rig gets good mileage if you go through BC. Their fuel prices are ridiculous, approaching absurd.