For people who are thinking "I like to try but i dont know how it will be useful since i use IDE XYZ all day", start with org-mode. Think org-mode as a tool to manage your todo lists, although it it much more than that.
To a developer not familiar with Emacs, I'd first recommend to start with Spacemacs so they don't have to configure anything nor learn Emacs shortcuts... then Magit (shipped as git layer in spa Emacs)... and then org-mode. I had a few developer friends of mine starting to use Emacs (Spacemacs) solely because of how good Magit is.
Projectile is a great tool too. Along with helm and perspective modes, you can switch between projects with a few keystrokes. Since projectile looks for .git by default, you can have a window in each perspective dedicated to git if you so wish.
Updating code across multiple projects and committing is so easy and frictionless.
Press C-z. Multiple edits can be achieved through marking in helm. I need to get a grips with this part myself - sometimes it's just easier to use dired.
Have you figured out how to switch between recent list and other match lists? Sometimes get stuck when a prefix matches bang on in recent and need to get to the other matches.