The problem with keeping Buenos Aires tetras with angelfish is that the tetras are fin nippers and would nip angels' big fins.
Some species of tetras can be kept with angels provided they are not fin nippers, swim sedately and don't dash everywhere at high speed, and are not small straight bodied (neon tetra shaped) or when the angels are fully grown they'll eat them.
Some species of tetras can be kept with angels provided they are not fin nippers, swim sedately and don't dash everywhere at high speed, and are not small straight bodied (neon tetra shaped) or when the angels are fully grown they'll eat them.