Should the letters be all lowercase? Does it matter? Can it be all uppercase?

Should the letters all be lowercase? Does it matter? Can it all be uppercase?

Hey, I have submitted some designs that meet your need; please let me know if there are any adjustments you would like, and I will make them right away.

I'm awaiting your swift and positive response.

kind regards.

Hey there, that doesn't matter, it's all about the total picture. Grtz, Arthur