A few degrees makes a pretty big difference when it comes to salmon. It's really a matter of personal preference. So it might take some trial and error. There are some sweet spots for salmon. I've found anywhere between 118 and 122 to be my favorite, because I like it pink in the middle. I don't reverse sear, because you lose the even, delicate texture you've achieved with sous vide. And it overcooks so quickly. If you decide to reverse sear, you'll want to use a much lower temperature, like maybe 108. You might gain different flavor with reverse sear, but you also lose texture and fat. It's a compromise.
Same thing as Eric above. I usually go with what's around the house, or in the garden to inspire me with salmon. Always a hunk of butter though. In the summer, I have every fresh herb known to man in my garden. Dill is of course a favorite, but tarragon, basil, rosemary, thyme are all good. I try to keep it simple with salmon. Just butter, salt, pepper, and one fresh herb. A slice of lemon is good too. Maybe a little sprinkle of garlic powder. Winter is a good time to experiment with seasoning blends from my spice cabinet. Mostly, I let the salmon be the star though, and don't over-season. Of course, a good hollandaise is always welcome on my plate, especially if I'm serving with grilled asparagus or some other grilled vegetable.