@qamzardaany
Yes, they speak Malay, they use a Malay-Muslim Script Jawi in their writings, it's different from the Tagalog Baybayin based on a Brahmic-Javanese Abugida. They still retain the use of their unique script whereas Tagalogs lost the usage of Baybayin.
Tausugs are classified as a Visayan people, same as the Christian Butuan, Cebuano and Hiligaynon. Tausugs are pro-Filipino since Filipinos are pursuing the historical claim of the Sultans of Sulu over Borneo using Filipino diplomats and former Dictator Marcos planned an invasion of Sabah in the name of the Sulu Sultan.
Whereas Maguindanao and Maranao people don't speak a Philippine-Visayan language and are more related to the Sulawesians of Indonesia and the Sultanates of Mindanao (Lanao and Maguindanao) was once allied with and under a federation with the Sultanate of Ternate.
Though all mentioned (In fact all Southeast Asian sultantes) speak Malay and Bahasa as the common lingua franca.