There are thousands of files on my various computers installed as part of the operating system or applications whose precise function I don't understand, and I don't generally need to. You claimed the files were not original to your system. I suspect that they are, more specifically they are part of your user profile, since I don't see the same set of files in the system library. The ~Library/Preferences folder is full of plist files. These are generally plain text XML files containing preferences for various applications and services. Unless you have a good reason for exploring this folder you should leave it alone. You should not edit or delete any file within unless you understand the consequences of doing so. Taking a look inside some of the files on my system suggests a connection with iCloud since my various email address and mobile phone number are listed in some of the files. Searching the web for details has proved fruitless, which isn't that helpful, although I would have expected to find something concrete if the files were a known cause for concern.
What makes you think the presence of these files is related to your difficulty logging into your iTunes account or screen sharing with Apple support?
tt2