Make apps smaller / "zoom out" apps I made my screen resolution much smaller, so now most apps look 4x larger than I'm used to.

iTunes and Finder for example are much larger than they need to be.

Can I make everything about these apps smaller?

The text, the window sizes, the icon sizes etc.

Macbook Pro w/ Retina display, mid-2015 15".

I used RDM to make my screen to 720p. Previously had been 1080p HiDPI
Go to the screen and right-click on the desktop. This brings up a menu and the last option is to "Show view options". Select this. You'll get a small window where you can adjust the icon size.

You can also change font size and icon spacing.