My Julie and I made the Alaskan journey twice, once in 2015 & 2018. Keep your itinerary flexible and as one of the poster said do Canada and Alaska first. In getting reservations for Denali good luck you'll most likely have to boondock which we did a lot of and there's lots of boondocking in Alaska and Canada.
I would suggest adding Tuktoyaktuk to your to see list unbelievable sights, in Canada. In Alaska add the Dalton (aka Haul road) to your list.
The days are long so you may find yourself driving longer than intended, Fairbank day was over 21 hours long when we arrived.
If you don't have them get black out covers for your windows.
Now for the Alaskan stat pest the mosquito bring mosquito netting it was the only that kept them off me.
You can't over stay unless you have trouble with cold weather.
Before I forget download iOverlander app. a good source of wild camping and just for the night places.