I personally just use phones built in weather widget. They seem accurate enough for timings but as far as an app telling you if its going to be a nice one I’m not sure. Probably better off using your eyes to see how clear it is an hour or two before hand.
I have used this one in the passed, it uses your phone camera with a sun trajectory overlay so you can see where it will crest and its movements thereafter. As for predicting when it will be picturesque I would check for a nice calm cloudless morning.
I use the Golden hour app seems ok to me
