Welsh Polytheism could fall under Brttonic Polytheism. It can also be its own thing.
The Welsh were a group of people living in Wales that split from the Brittonic peoples.

Many Brythonic territories fell under Anglo-Saxon control after the Anglo-Saxon invasion of Britain; however, Brythonic Celtic religion was largely preserved in Wales. Since several Welsh myths were later Christianized, determining if the characters were actually gods, mortals, or historical figures may be challenging.

Welsh Gods and Goddesses

Gofannon – A Smithing God.

Ceridwen – A goddess of rebirth and transformation.

Amaethon – god of agriculture

Creiddylad – goddess of flowers and love

Gwydion – magician, trickster, and hero.

Agrona – goddess of the river Ayr, and of war and slaughter

Arawn (Arawen) – king of the otherworld realm of Annwn

Branwen – goddess of love and beauty

Welsh Resources

Welsh Myths and Stories

The Four Ancient Books of Wales – https://tinyurl.com/4ya2pax4

The Mabinogion – https://tinyurl.com/4wsudyxa

Introduction to Welsh Polytheism