Is it sufficient for a Muslim to say, "I am a Muslim," when identifying their belief, or should they say, "I am a Salafi Muslim," if their creed conforms to the creed of the righteous predecessors?

It is sufficient for a Muslim to say "I am a Muslim" to make their belief known. If they add "I am a Salafi Muslim," there is no harm, provided that by Salafiyyah they mean following the methodology of the Prophet (peace be upon him) and the righteous predecessors of the Ummah, including the Companions and those who followed them in goodness, in belief, action, and conduct. Salafiyyah in this sense is the true methodology that every Muslim must adhere to. Sheikh Ibn 'Uthaymeen defined Salafiyyah as "following the methodology of thef predecessors in creed, word, action, disagreement, agreement, mercy, and affection, as the Prophet (peace be upon him) said: 'The example of the believers in their mutual affection, mercy, and compassion is like that of a single body; if one of its limbs complains, the rest of the body responds with fever and sleeplessness.' This is the true Salafiyyah."