Is Salafism a sect more specific than Ahl al-Sunnah, and are its principles based on the views and sayings of the sheikhs of this sect?

This statement is incorrect. The Sunnis follow the Companions and the Salaf, and they are not separate groups. The Salaf are the Companions and those who followed them. The Sunnis are those who followed the Sunnah of the Messenger, may Allah bless him and grant him peace, and they are the saved group. It is not permissible to stir up discord over mere titles. A person's intention should be truth and justice, and their hatred for anyone should not lead them to reject the truth or seek out faults. A Muslim must love for his brother what he loves for himself and be a sincere advisor to him.