Hurricane Ridge was by far the biggest climb I had ever done (previous being a measly 1,600 feet in State College, Pennsylvania). It wasn't hard to pace though, as the gradient was never very steep (18.7 miles at 5%, starting from downtown Port Angeles). I saw almost no other cyclists surprisingly (this was mid August). From what I can tell it is a pretty famous climb and there is an annual ride up it "Ride the Hurricane" with no cars allowed. I did encounter a decent amount of traffic but never felt unsafe.
Below is the view from the Visitor Center where you can get snacks!
Obstruction Point Road was a lot harder than I was expecting. It is about 7.5 miles long, with 1,200 ft gained on the way out. The first section is mostly downhill but is very washboarded. That is followed by two relatively short but steep and loose climbs, and one longer one (.7 miles at 7%, 1.7 miles at 10%, and 1 mile at 7%). I was pretty tired already and over-geared with a 34-32 minimum. Going back down was a bit sketchy and I almost lost it once. Doing this with road tires/gearing would be real hard, which I guess is why the main Hurricane Ridge Road segment has ~1,700 people and Obstruction Point Road has 17. It was probably mostly hard because I'd just ridden 5,000ft at a sustained pace (think I did 228w for a little over 2 hours, and my best 20 min power is a little over 300w).
Going back down Hurricane Ridge Road was nice, although it wasn't steep enough to simply get into an aero tuck and coast, so I ended up pedaling quite a bit on the way down. Still, cruising downhill for that long was fun; especially the twisting bits near the top. The total elevation was 7,800 ft in 52.7 miles, which was quite a lot for me. The weather was very nice.
If I had it to do over again (which I do this coming summer) I'd lower my gearing (new low is 34-40) and maybe try to time it so that Obstruction Point Road is a bit more hardpacked and less washboarded. The tires I used were a good choice I think (38mm Schwalbe g-one allround tubeless). I wouldn't go narrower or knobbier.