Historically at this point there was a large group of Goths living in Septimia.
And what about the Arianism of the Vandals?
The Visigoths in Septimania fled to Perpignan in the face of Moorish invasion, and the remaining were mixed with the Frankish used to blow up the walls of Perpignan using naptha. The Visigoths inside the walls either fled or died. The Vandals really hate them Visigoths.
As for Arianism, Hilderic was overthrown by the Arian faction of Gelimer, and had previously converted.
Thanks for commenting, dear Finn!