I love my 7/8s violin, But I also Love my full size... I believe that it is impossible to love just one, because, just like people, they come with so many different personalities so you can love them in so many different ways. My solution to this one has been "never limit yourself to just one violin". I also find that some days I'm more in the mood for the 7/8s than full size and vice versa.
However, I'd say travel around if none of the violins at the local shop suit you, because, of course, the more broad the selection, the more likely you are to find that love of your life.
As for setup and strings, most shops will have set up the violins to bring out their best traits, and likewise with the strings. So if you like a violin enough to buy it, then swapping strings will probably be more of a personal taste issue
I don't think I could ever sell the violin I currently play, but I may surprise myself one day. I will most likely just add to my collection.
P.S I just switched from evah greens to Warchal Ambers on my main violin and I am loving them