Is hint for translator compulsory while internationalizing a string containing variables?

I am following this official guide to internationalise my plugin. But I am confused if the hints are must required incase of variables inside string?

Also in this documentation, no where it is mentioned to use load_plugin_textdomain to load the text domain. It is only mentioned about the Domain Path. So can I omit load_plugin_textdomain if I use Domain Path?