All the fonts on my 4k monitor are too big because my 4k monitor is detected as a 27 inch monitor instead of a 32 or 40 inch monitor.
This will change things like the Chrome Tab font size.
The Dots per inch resolution is buried, here is where to find it.
System->Preferences->Look and feel->Appearance
Click the Fonts tab
On the lower right click on Details
Which brings up this screen, turn off Automatic detection under Dots per inch (DPI) and change it to 128 or 136