Upload & Sell: On
you seem to like the "long", more pano format, but I am not sure you need to take off the top. And you might end up with a more standard aspect ratio, always cheaper to frame.
There are many, many different ideas about print resolution but there are many variables as well.
Type of paper: Glossy needs more sharpness, higher res. Matte is more forgiving. Canvas more painterly still, less detail preserved typically, can go lower res.
Subject: Portraits can often be low rez. Unless you want a detailed gritty look, lower res is fine. And for beauty and women's portraits, kids less detail is often better.
Landscapes are typically viewed with expectation of great DOF, high detail and need tons of resolution.
Architectural shots vary but often can be lower res as long as there is strong edge sharpening applied.
Viewing distance: This is one place where people fret too much. While most of us and some of the general public will try to get as close to an image as possible, seeking out detail, especially with landscapes, in most situations photos will be viewed from a couple of feet away or more, further the larger the print. Closely viewed images need more res.
Where does this go? I print a lot of bird images at 12x18 on glossy papers. Well-captured images with excellent sharpness, detail often come off of a 200 pixel/inch file, uprezzed by the printer. Below 180 pixel/inch I would always uprez in PS first. I just did a 12x18 print from a heavily cropped capture, yielding a 6 MP file. After uprezzing my friends decided to get it. I thought it was a bit soft. My wife said no.
Yours? I would uprez. Probably shoot for 14" on the long edge. By personal satisfaction with the image is another variable. With good uprezzing, maybe a bit more on lustre.