The OnScreen Display Settings are accessed by touching the touch sensitive button next to the Power button.
There are just a few places to change in the default settings, circled below in red. They are basically the same for the DisplayPort and Mini DisplayPort. The only differences I found are that for the Mini DisplayPort connected to the iMac the Sharpness was better at 50% and the Input Source in Color Settings works better with RGB (while the DisplayPort, connected to the MacBookPro, prefers YPbPr).
The two shortcut keys provide quick access to specific settings. As I most often just want to switch between my two computers, I set them up like this.