I have yet to land on the perfect setup for fishing and hiking, but I've tried a number of different pieces of gear or combos of gear over the years.
It's the rare vendor that effectively combines the best of a backpack (good waist belt, padding, adjustable, air flow) with a fishing offering and so for anything that is a full day or longer, I use a hiking backpack and a small fishing chest pack. I have not found a fishing pack yet that allows me to carry enough stuff for an overnight outing, even if I pack ultra-light. The William Joseph Exodus looked like a winner and I bought it based on advertised size of 3000+ cubic inches. But when it arrived, it clearly fell far short of that size and the vendor confirmed via email that the size was a typo. It still works well for an all day trip and I dusted it off and used it again a few times this past fall.
I have a few GoLite Jam ultra-light backpacks that I use for all day trips and they also worked for an overnight trip too. The problem with them, especially for overnight, was they didn't fit my torso and waist properly and weren't adjustable, so I went back to my old standby vendor for packs which is Gregory. Then I carry a small chest pack, generally large enough to hold a couple of fly boxes, tippet, hemostats and some shot. If I'm overnight backpacking, I can drop the main pack at my camping spot for the night and continue fishing upstream without a lot of extra weight.
I have a few of the William Joseph chest packs as well - Coastal, Coastal II, Confluence, etc. Each is ok, but I end up going back to the backpack and small chest pack combo as my preferred setup for anything longer than a few hours.
I recently picked up a Patagonia Hybrid Pack Vest on half-price closeout and I really like it so far. It encourages me to pack sparsely, but has enough room to carry everything I really need on a one day trip if I make wise choices about what I'm carrying (I don't really need to carry four fly boxes!). I've only used it once in the dead of winter, so maybe my opinion will change in the heat of summer, but it is not bulky and doesn't have junk hanging off it everywhere. I didn't catch on trees as I ducked under them or get caught on trees a I climbed over them. The only thing I don't like is that it is a bland one-tone light color, which seems like it would be pretty easy for a trout eye to pick up as it moves towards them. A nice tactical camo would be perfect 🙂
Packs, vests, or whatever you use to carry your gear and clothes and food and drink while on the stream end up being a personal preference. You'll end up collecting a few most likely until you figure out what your preference is.