Have a few weeks to kill so went about a third of the way up road 35 the other day just to see what has changed in 6 years. Bitumen goes a bit further north of Gullfoss and there are three lots of pony rides, glacier walks, boat trip+glacier walk, hostel, restaurants, nice campgrounds, regular scheduled passenger buses, heaps of tour buses and heaps of bigfoot jeeps all mixing it with a stream of bike riders, motorcycle riders and small 4wds plus a lot of small sedans doing their best not to void their insurance and of course a regular stream of small and medium motorhomes. AND two graders doing their best to fill in the connected potholes with fist-sized rocks spread right across the road to give the bike and motorbike riders something to concentrate their survival instincts on. Certainly a lot harder to feel you are the only one within a 100km than it used to be. We pulled up for coffee at one of the very few laybys, and within a minute we were joined by two full-size passenger buses, a motorhome and two cars
Talked to a Swede who hired a Suzuki Jimney and he had just made it down F25, albeit only by driving across one river that came up to the bottom of his windows. Takes all kinds! He said that river had a ranger stationed there to tell the drivers the best way across to avoid the deep holes and big rocks.
Yes, looking at the tour guide info I think you will be happy to be able to concentrate a fair bit of all aspects of Iceland into a relatively short time.
Have fun.