So what's the best now in the game? So far I've found the Dwarven Bow and the Elven Bow. The way I see it is the Dwarven melee weapons are stronger, and the Elven bows are stronger. Is that right?

The best I've found is the Ebony Bow. I have found a single Daedric Arrow over the past in game month, and fired it off in the hopes that the universe would give me more if I used it. No luck... Shoulda given it to the training soldier in Solitude, I don't know why I didn't think of that until literally just now.

Is the arrow valuable?

The Daedric arrow is the most powerful arrow in the game (to my knowledge) I use a daedric bow as it looks beautiful and much nicer than the Ebony bow in my opniion. But my bow is unenchanted as i dont want to have to make another if i want a different enchantment.