Cymry are the people of Wales (Welsh). Same pronunciation as Cymru (Cum-ree).

The other definitionis right, but you wouldn't say "Mae'r Pobol Cymry yn brydferth iawn!". You don't need the word 'pobl'.

A very smart and beautiful girl with a great big heart. She keeps a low profile cause she doesn't want to blow her cover. If the secret service found out that such a person exists they would destroy her and all man kind.