I think excersises are like practicing particular words or combinations of words, where playing music is words put into sentences. You might be really good in saying particular "musical words" but if you don't practice it in a "musical sentence" you can sound very forumulated. It is like presenting a speech but doing it in a boring way because you only memorized the words not the message and expression behind it.
Putting pieces on the wall is helpful for us to get an overall picture of the piece that we study. It helps us to visualize the overall memorization of the piece given that we have highlighted patterns and sections etc. When we look at them we should be able to hear that section in our minds eye, our Sound memory should be influenced every time we make an observation of the patterns we have sectioned in the score out. Seeing the entire score simultaneously, colored out and sectioned out in a way that is logical and understandable for yourself is helpful especially when learning large scale works. Many people approach learning music by doing page one and not moving onto the second page until they have mastered the first. So pasting up your music forces you to observe your music all at once breaking down the security blanket of doing everything safe and one at a time.
I would have to say to play a piece properly one has to emotionally connect to a piece. There are many shades of emotions, if we simply consider everything on terms of loud soft, fast slow, then we can miss the more spiritual/emotional side of playing the piano. Something may sound sad, but what if the sadness is more reminiscent of the past instead of a loss of the present? Is there a difference? I would say so and music can inspire these different shades of similar emotions. Like for instance Chopins Ballade No 1, much of it sounds like an old person thinking about their past long gone and it seems that the entire piece highlights their memory of the past and how now its all gone but back then it was so great!
One can make up any story they like, what is important is that they can emotionally connect to it, thus the abilty to present the music becomes more natural and from the "heart". Ondine from Ravel is easier to understand because there is a poem that is attached to it, so when that single note phrase is played near the end do we simply think, oh slow and gentle here, or do we think of tear drops dripping one by one into the lake because the spirit was denied love? Then do you simply think, arpeggios now follow or do you think, the immortal spirit gets up laughs it off and dives back into the water deeper and deeper never to be seen again.
I think images speak one thousand logical words. Of course this only applies for those with a more advanced ability, it would be hard for a beginner or intermediate to do this effectievly but they can still do it in smaller situations. I usually tell beginners who learn little ABA form pieces, to think of a sandwich, for example play part A Forte (eg an image of hard stale bread), have a very quiet middle B part (soft fillings), then end in the same forte fashion. So I don't have to say play this bit softer I just say have to say, Oh now we have reached the middle of the sandwich, which makes them understand they should play softer, noticing how that phrase is softer than the first part but that they should expect the first part to repeat again to complete the sandwitch. Always having your mind in context to the entire piece using imagry and symbols is very helpful and can be used at all levels. This is something that can only be trained with pieces however.