The thing nobody tells you about landscape art is that it reads as a view, not a picture, so your brain wants it to make sense the way a window would. That means horizon lines matter more than frame color or subject. A print with the horizon sitting too high or too low on a wall that's already an odd shape will nag at you every single day, even if you can't say why. Get the horizon roughly at eye level or just above, and most other decisions sort themselves out.
Measuring for this is less about the wall and more about the furniture under it. I made the mistake of hanging a wide, low landscape over a narrow console table once, and it looked like the print was wearing shoes two sizes too big. The rule I use now is that the piece should run about two thirds to three quarters the width of whatever it's hanging over, whether that's a sofa, a headboard, or a sideboard. Measure that first, then go shop, not the other way around. And don't be shy about scale. A small landscape alone on a big wall looks like it wandered off from a gallery and got lost, it needs either real size or real company, a second piece near it to anchor it.
These work hardest in rooms where you actually sit still for a while, living rooms, bedrooms, the end of a hallway you pass a hundred times a day and never quite notice until something's there. A calm, wide landscape over a bed can make a small rental bedroom feel like it has more air than it does, which matters a lot if your actual window looks at a brick wall, mine does. They also suit homes that already lean a little quiet, mid century pieces, worn wood, linen curtains, anything that isn't shouting. In a kid's playroom or a kitchen full of bright pattern, a moody, muted landscape just goes flat and sad, like it wasn't invited to the party.
Where it really struggles is next to anything else demanding a long look, a gallery wall of family photos, a bold patterned rug underneath, a room that already has a statement anything. Landscapes want quiet neighbors. Put one across from a loud accent wall and your eye never settles on either, it just bounces.
The one mistake that ruins all of it, though, is hanging it too high because you're matching some imagined eye line from a showroom. Hang for your actual room, at your actual eye level, sitting down if that's where you'll be looking at it from.