I never really paid attention to what you just described, but here is my take on it. And yes, I see the same things.
Some people have User Names that are different from their "normal" name. For example, Mary Smith could be "Sky Pilot" on Skype. The entry on the Contact card allows for this information. And this user name could be for a work or home (non-work) account, hence the options.
Regarding the "FaceTime" line, if the mobile phone number is an iPhone, when you hover the cursor over that line, the option to make a FaceTime call, either audio or video, to the person is available. This is a nice feature that avoids the need of a cellular connection and relies only on an Internet connection. Useful for international travel or when calling from a non-cellular device, like a computer.
On a Mac since 1984.
Currently: 27" iMacs, Macbook Air, macOS 10.15.x,; iPhones, iPods and iPads galore!