Are Pokemon VMAX considered as "Pokemon V" for the purposes of Boltund's "Fighting Fangs" attack?
Yes, Pokemon VMAX are always considered to be Pokemon V.
Fighting FangsPokémon V



x2
Big BiteDuring your opponent's next turn, the Defending Pokémon can't retreat.


Fighting FangsIf your opponent’s Active Pokémon is a Pokémon V or Pokémon-GX, this attack does 90 more damage.
This Pokémon generates electricity and channels it into its legs to keep them going strong. Boltund can run nonstop for three full days.
Are Pokemon VMAX considered as "Pokemon V" for the purposes of Boltund's "Fighting Fangs" attack?
Yes, Pokemon VMAX are always considered to be Pokemon V.