Default protocol when using command line

What default protocol is used when I issue a command like

winscp user:password@ftp.xxx.com /command "put c:\temp\file.log incoming/file.log" exit

It is configurable. By default it is SFTP.

Do I assume correctly that this is goverened by the protocol saved in a stored session?

The defaults are governed by the default session settings that can be set on login dialog.