The artist, Adrea, doesn't need much details, quite the opposite. He seems to flurish the less details he has. I still do a minimum but will probably change some details here and there.
Basically, Neighsay and Cadance explore Cadance's memory for a specific untold purpose. Until we assist to the dragon fight, where Neighsay manages to help Shining Armor's mentor to defeat the dragon, where Neighsay realises that he was searching a specific form of a teapot.
For what? To make one by himself and to give it as a gift to his wife, the same lady he couldn't talk to without screaming.
Why are they in love? Well, at some point, Cadance just used her magic of love on them. Seems love can resolve anything, isn't it?