As usual, gear choices are highly subjective, and how you use gear is likely more important than the exact gear you use.
Alaska can often be rainier and windier than some places many of us are accustomed to, and the consequences of getting too cold and wet are more serious because bail-out options aren’t as readily available.
My standard gear for August in Alaska includes a Lunar Solo or a Tarptent. I’m careful about where I set up, and those shelters have always worked well for me. If you have a lot of experience and will have access to wind sheltered areas (I commonly camp in openings in willow thickets or spruce trees) light shelters should work fine for you.
My standard sleeping bag is a 20 degree down bag which I’m careful to keep dry and has always kept me warm. A 32 degree quilt might work, but will be marginal, at best, if you are tired, wet and chilled. You know how it is with temperature ratings: major subjectivity.
I use standard breathable rain/wind gear. Personally, I absolutely would not choose an umbrella for Alaska hiking as it wouldn’t mix well with wind and/or brush.
The ground will be wet a lot in many places. I usually use light, broken-in, high top leather Gore-tex boots. If there’s a perfect type of Alaska backpacking footwear, I have yet to find it. Often I can keep my feet dry (at least for a while!) in wet conditions by blousing my rain pants over the tops of my boots with rubber bands to keep water from splashing in. It can even work for a few steps in barely-over-the-boot-top water. Sometimes.
Late August tends to run much cooler and less buggy than early August of course. A good rule of thumb in Alaska is to always carry DEET except in the winter. I have run across bad bugs in Alaska in August many times.
I was in Washington on the PCT in September this year (think wet and chilly weather a lot,) and would be perfectly comfortable using that same gear in Alaska in August.
FWIW, here’s my gear list from my Alaska traverse.
This looks like another well thought-out list.