Is there any difference between default scp and PuTTY pscp (with -scp) protocols?

... if there are minor details that I'm not aware of (performance, security etc)".

There are none. scp (Secure CoPy) is a protocol and command line utility for secure file transfer; and pscp is just the name of PuTTy SCP/SFTP client. The security of SCP is provided by SSH, which is used for data transfer and authentication.

The fact that the file provider manual already includes pscp is just a nice gesture from whoever is responsible for creating it. It being specified in the manual signifies that the creator usually deals with Windows users. Unlike UNIX- and Linux-based systems (including MacOS), until Win 10 Windows OS used to not have an SCP client.