I beg you, if you are a developer of an open source app or program - add screenshots of your app to the README file. When looking for the perfect app, I had to install dozens of them just to see what the user interface looked like and whether it suits me. This will allow users to decide if the app they choose will suit them… Please, don’t think about it, just do it…
Define “best” for every single program.
There is no general best. If there were, it would be easy for the dev to set it. Different people have different ways of using software, so there is no best.