I love Iceland!! I found Rick Steves' Iceland book very helpful, just fyi. Have so much fun!!

Other than REI, I've had some good luck at Bass Pro Shop, and Columbia/EB/etc outlet stores, if you don't want to spend a fortune. There's also Sierra, the TJMaxx of active wear

Consider if you want waterproof or breathable, and ankle high (support against twisted ankles) or something lower profile that will be lighter (and smaller, if you're packing them).

Honestly, as somebody who is not an expert but likes to hike occasionally, just find something that feels good on your feet. Anything at REI is probably going to be good quality. I've gotten shoes I like from Columbia, Merrell, and Eddie Bauer

The last wedding I stood up in, we got ours from Azazie. They have a try-on program where they'll ship you 3 dresses for $20.

It does suck! I find that a baseball-style running hat helps me, if you haven't tried one yet. The bigger the brim, the better.