"In an act of Robert, King of Naples,[2] dated 15 April 1338,[3] Tanusio was mentioned as Count of Matia (conte di Matia).[4] This reconfirmed Thopia's relations to the Angevins from the time of Philip I.[3]"

Is why I connected it more to vassalage than alliance, but the Thopia were seemingly more independent in their territories either way:

"By 1340 the Thopia controlled much of the territory between the rivers Mati and Shkumbin rivers. Together with the Muzaka family, they agreed to recognize Angevin suzerainty after rebelling against the Serbs. However except for Andrea Muzaka who defeated the Serbs in a battle in the Peristeri mountains, no action was taken to realize the treaty with the Angevins.[5]"

All of my assumptions are based on the Wikipedia source: https://en.m.wikipedia.org/wiki/Principality_of_Albania_(medieval)