Climbing out of Benson Lake is a real bear, and takes me about a half day to get out of that basin to Smedberg Lake. I would never dream of trying to get to Pate Valley from Benson in a day, but I do carry a heavy pack. There are some good places to camp once you get beyond Smedberg Lake, including Rodgers and Neal Lakes. When I went through there I camped in Rodger’s Canyon by the creek just off the trail before reaching the GCT rim. There are no great views there, but it’s very quiet and peaceful. It took me 4.5 hours to get from that campsite into Pate Valley by the bridges over the river. Getting to that Rodger's Canyon campsite from Benson Lake would have been a good 6 hours if I recall correctly. The trail is very well marked until you reach the rim, and then parts of it along the rim are overgrown with bushes here and there until you reach the switchbacks down to Pate Valley. You probably won’t lose it, but you will have to spend some time looking at the terrain to stay on it and make sure nothing is hanging out far from your pack. The drop into Pate Valley is very hard on the feet and takes a couple of hours. When I did it in 1999 I was up against an impressive fire on the other side of the valley that was burning its way down the steep ridge from Hetch Hetchy, so I didn’t investigate any possibilities of camping on Piute Creek. I remember it had water in it late in the season, and the area had a lot of trees with one open meadow with tall grass (over a foot) in it that was perfect for landing a helicopter. The nicest campsites I recall were along the Tuolumne River on both sides of the footbridge, and I’ve camped on both sides. Just remember the area is as hot as hell on a summer afternoon (around 90 degrees F) and loaded with snakes. If the bridge is out, getting across the river can be dangerous even in a drought year due to the strong current. It’s the hardest river crossing I’ve ever done in my life.
Conness Creek and Return Creek should flow all year, but don’t count on any significant water in between them, as the seasonal runoff should be over with by now. There should be some puddles here and there as you go upstream farther along the feeder creek to Conness Creek. I have seen a little water flowing there in August, but it wasn’t a drought year. If you have a pump with a filter you should be fine, and a cup could probably scoop water out. I personally prefer the Glen Aulin High Sierra Camp, as there are some isolated campsites there are aren’t used often except on weekends, and you have plenty of water in Conness Creek. It’s the only High Sierra Camp in the system that I like.
Miller Lake is a campsite used by mule/horse tours that go down that section of the PCT (complete with fences). I did not enjoy my night there as the stock roamed freely and kicked up dust all the time. Otherwise it is a nice lake. I enjoyed camping in Matterhorn Canyon much more, which is amazingly quiet.
Return Creek is the only crossing you might find slightly challenging, but you’ll probably only get wet halfway to your knees worst case due to the drought. The real challenges are in the Jack Main Canyon area that you are staying away from.
All trail junctions are clearly marked with the trademark Yosemite signs that the letters are punched through metal. I haven’t done the High Trail yet, but the pictures I’ve seen show it clearly visible. If you have problems with the trail, it will likely be when you come down from Red Peak Pass. I haven’t done it since they redid the trail, so hopefully it is better now. It was one of the worst marked trails in the park and extremely easy to lose in snow by following the wrong footprints. It didn’t follow a logical route in those days. The rest of your route is well used and marked.
Downed trees have been the biggest issue for me since the long drought ended, as about 1/5 of the trees appear to have died and they do fall eventually. The park does use a few men with chainsaws to cut the ones across trails, but it takes them most of the summer to get all the trails done. If you go off trail, you may be slowed down considerably by these trees. In forested areas when I’m off trail, I hit one about every 2-3 min, and some require long detours due to their size.
As long as you don’t run into a bridge that is out over the Merced or Tuolumne River, you shouldn’t have any hazardous water crossings due to the drought this year and the time you are going.
My understanding is that all the backpacker’s campgrounds are open for backpackers to use for one night at the beginning or end of your trip - Hetch Hetchy, Tuolumne Meadows, and North Pines (Valley Floor). They are audited by rangers, so have your permit with you. The bathrooms may not be open, but you can get water from the river nearby (Hetch Hetchy might be difficult to do that at) and follow standard wilderness practices.
The TM store usually opens a week before the campground, which is not going to open until August 1 per the latest news. Bear lockers are at all the trailheads, so that’s the only alternative if the store is closed. The closest lockers to the store are located across the street on the other side of the river, along the dirt road that is used for the Soda Springs trailhead parking. It’s a 5 min walk from the store.
I don’t think any place that offers public showers will be open in Yosemite this summer due to their social distancing guidelines. Housekeeping Camp on the Valley Floor is the most likely one, but it’s a long walk from North Pines.