1. I'm a long time Emacs user (30+ years) and a professional developer. Trying to contrast one of these versus the other as you do twice in your comment isn't really helpful or useful.

2. Why would I want to put a tooltip over an emacs window?

3. The things that contemporary IDEs can do that Emacs may be clunkier at are mostly things I'm not interested in doing. They are also often addressable in totally different ways. The speed of tools like ag(1) and their integration into Emacs changes the need for Emacs itself to be able to take me to special places in a codebase, for example.