I’m thinking that perhaps dream recall can be used to learn about suppressed or hidden aspects of oneself. Some of my most pleasant dreams involve a kind of euphoric feeling from natural beauty. It’s strange, because I’m not nature-inclined in WL, but sometimes in dreams I find myself next to a river under a clear and sunny sky, or a beach during a windy dusk, or a mountainside overlooking the sea during a vigorous trek, and get this blissful emotion. I wouldn’t react like that in WL. So, in what ways does the dream self tend to differ from the WL self for other people? Anything useful or interesting you’ve learnt about yourself from recalling your dreams
Well, I at least try to be violent in my dreams (doesn’t always work well though), but I’d probably just hide if I found myself in such situations IWL. Also, in one of my recent dreams, I’d been given a baby to take care of. IWL, I say I don’t want children. However, even after waking up from this dream, for the next day and a half, I was in a strange mood since I was missing the baby from the dream. I believe dreams are a way to be able to explore sides of yourself that you can’t normally express or don’t even know that you have.
I have also noticed differences of self in dreams, but the only time it has been really clear was when I had my first big LD. I talked in flowery language, was very peaceful and happy, and had blond hair for some reason. For the emotional things - I tend to be decisive and care about justice and judgment a lot more in my dreams. I’m not talking about hellfire and damnation, but instead my dream self seems to have extremely well laid out ideas about morality and beauty - hence the recurring activity of pausing a dream to consider whether or not some activity (Killing someone, for instance) was a good idea or not. Part of why I want to get good at LDing is because I want to understand more of that aspect.
As humans, we are capable of thousands of different personalities and perceptions, and we are constantly shifting in and out of them. In our dreams, our minds already know this, so we merely shift from one possible personality to another.
I can be a cold blooded killer, a nightmare creature, or an angel, a helper, a saint.
I’ve noticed that my emotions are much more pronounced in my dreams. IWL I’m much more guarded about how I feel, but in my dreams I let them go wild a lot more often.
I can’t say I have experienced this very strongly myself, or rather not as far as I can remember, but I think I know what you are talking about.
I think, as said here, that has something to do with exploration. As Dazino said our human mind has many ways to act and react, and it is making choices all the time.
We nowadays think that dreaming is a way the brain wraps up the events of the day, that it deals with them and it stores them. Couldn’t it just be that part of this wrapping up process is going over them again, testing out different ways to react. Practicing so to say. Wouldn’t that be a way for the brain to decide if it’s actions in the past were correct, and so how to behave in the future.
I really believe our brain is learning all the time, adapting to stand a better chance in the future in whatever is thrown at us, so I think there might be something to this.
I’ve noticed the same in my dreams.
IWL my emotions feel kind of … grey, sometimes. Nothing special. Sometimes I can get strong emotions (usually negative 
) but in my dreams, sometimes, it goes beyond that. Like “deep” emotions. For example, IWL I’ve felt, every once in a while, strong emotions of sadness or loneliness, but in a few dreams, these emotions become deep sadness and loneliness and melancholy 
But oh well! I can also get really angry in my dreams. I am a lot more assertive and face people or situations when I find them unfair in my dreams (something that I don’t do IWL, but really bothers me).
On the other hand I’m also able to feel deep peace and love. I remember a few lucid moments which were very vivid and beautiful, full of color and light, that made me literally fall to my knees with tears in my eyes 
I’m usually either a nightmare shadow or a mathematician buddha, with few inbetweens. My dream personality is usually pretty close to my WL one.
I do pay more attention to the other senses, tho. Normally, I’m a very visual guy, both with my physical eyes (which give perfect Legolas vision), and in my mind’s eye (where I can fly around high dimensions and algebraic structures as easily as the 3D euclidean space we usually live in). In my dreams (specially LDs), however, I’m usually more marvelled at the feeling of, say, wind or grass, than at a beautiful sight.