So....
I live here, so have no particular expertise on the RV infrastructure, but offer a few more thoughts;
- the pictures posted by TrackRig (Denali Highway? Tok Cutoff? Nabesna?) are what Alaska is all about IMNSHO. Call me biased, but that's the best of Alaska, particularly if it ends with a 54" + rack on the back.
- That being said, maybe those pictures aren't what attracts most RV'ers.
- The "road system" in Alaska can be navigated by a smaller MH or smaller RV trailer with some cautions: The Taylor tends to get narrow and muddy in the spring / fall; The Edgerton can be soft in spots in the late spring; Denali can get snow earlier than the main roads (Parks Highway / Richardson Highway) that are on either side of it.
- The main road system (Glenn Highway: Los Anchorage - Glennallen; Parks Highway: Wasilla - Fairbanks; Richardson Highway: Fairbanks-Delta-Glennallen-Valdez; Dalton Highway, the southern part) is suitable for RV / MH travel. There will be bumps in places and possible snow in late September, but I wouldn't skip RV'ng in Alaska because of fears about the main roads
- The secondary roads: Edgerton, Denali, Taylor, etc have some issues but can be RV'd with some planning, inquiry, and pre-trip thinking. The big issue is that rental companies tend to restrict one from taking the rental rigs on these roads. Just like anywhere in the Western US, there are some roads that are "do-able" but may not make sense to take an RV on. Alaska has some of those types of roads
- September (with the current climate, edging into October) is my absolute favorite time of year in Southcentral Alaska. A crisp fall day makes the snowcovered mountains pop out and the bugs (and most tourists :) ) are gone, it's hunting season and the less-crowded time to go fishing. If one RV's in a self-contained way, particularly if staying on the "main road" system, September is very RV'-able if you keep an eye on snow at the higher elevations.....but August would be some degree less "care-ridden" and would have much more to offer in the way of RV infrastructure if needed.
- Having traveled to/from Los Anchorage from the L48 some 20+ times, while I won't admit that there is better scenery anywhere than Alaska, the Northern Mountain West in the US and the trip up through BC and the Yukon are all very scenic areas. Every time I pass through the Kluane / Destruction Bay area, most recently in 2018, I can't help but go "WoW".....