Assalam alaikum,
Tasawwuf is non other than the inner, spiritual dimension of Islam. The tariqah--as method--is the attempt to both preserve and penetrate that dimension. The Shari'a is the Divinely Ordained mould within which that spirituality takes on its distinctive shape. These 3 aspects (Tasawwuf, Tariqa, Shari'a) of Islam are inseparable parts of an organic whole.
Imam Malik (may Allah be pleased with him) put it well when he said:--"He who learns jurisprudence and neglects Tasawwuf becomes a reprobate; and he who learns Tasawwuf and neglects jurisprudence becomes an apostate. But he who combines both will reach the Truth. As for the many paths which have developed over the centuries, the Classical Sufi saying sums it up:--"Tawheed is one, but the path to Allah equal the number of people since the time of Adam, peace and grace be upon him". These different ways have always been viewed as a mercy by the Ummah.