So here are some of the designs and features I build into my instruments and what I believe they add to the guitar:
While arching the top and back adds strength it also stiffens so as with many things a compromise must be made and mine is typically a 40 foot radius top and a 20 foot radius back. I have however used even larger radius on smaller bodied instruments.
Strings move the bridge and the bridge moves the top and that movement produces sound. There are many styles and shapes of bridges out there but I feel that a simple rectangular bridge is best able to move when excited by the strings and thus is best at transferring energy to the top so my bridges are all pretty simple clean lines.
You could write a book on guitar bracing, but my very basic thoughts are a good guitar can be built with any of the bracing schemes out there. Kasha, Martin X, Ladder, V, H, Fan, Lattice, Falcate and I'm sure others. All have been used to produce great guitars with their own sound. In my opinion the key is to decide on a bracing style and work to understand how to use it to achieve the sound you want. For my guitars I use a double X brace on steel strings and a 5 leg fan on nylons in general.
My necks are bolt on with a raised fretboard and I believe this has several advantages. First the neck is removable for repair or reset so this adds to the longevity of the instrument. Second the raised fretboard has several advantages. It allows for easier access to the lower frets without a cutaway and when properly braced it allows for more movable area in the top.