So you're basically discovering what we call the crop factor. Since the a6400 has an APS-C sensor, it's smaller than a full-frame sensor, so it crops the image coming through the lens. You're spot on... a 50mm lens will look like a 75mm lens would on a big professional camera. In my experience, 75mm is amazing for headshots, but if you're at a wedding and trying to get more than just a face in the frame, you'll find yourself backing up into walls constantly. It's just a bit too tight for indoor stuff or narrow streets. If you want that super blurry background but still want to be able to use the lens for walking around Maine, I've tried many options and I'd go with the Sigma 30mm f/1.4 DC DN Contemporary Sony E. It fits your $350 budget perfectly and that f/1.4 aperture is gonna give you way more blur than a standard kit lens. Over the years, this has basically become the must-have lens for Sony a6000-series owners. It's sharp as a tack and the 30mm focal length, which acts like a 45mm, is much more natural for general shots. If you're really dead set on those tight, creamy portrait shots and don't mind standing far away, the Sony E 50mm f/1.8 OSS is a solid second choice. It's cheaper, has stabilization, and the background blur is beautiful, but it's just much harder to use for everyday stuff. Honestly, go for the Sigma 30mm. You wont regret it for a trip like this tho.