The Welsh town is New Quay (2 words) and the Cornish town is Newquay (1 word).
There is currently a set called NEW QUAY, REAL PHOTOGRAPH
https://tuckdbpostcards.org/sets/41662
This set includes postcards of New Quay Wales and Newquay Cornwall and all cards for both towns have the NQ prefix.
I would respectfully suggest that the Newquay Cornwall cards should be moved to a different set name using the correct one word spelling. At present all the Newquay cards don’t appear in a search for Newquay as the individual card details don’t include Newquay.
There is an existing NEWQUAY & district, REAL PHOTOGRAPH set but all the current cards in that set have a NY prefix.
https://tuckdbpostcards.org/sets/41720
There are 19 cards for Newquay Cornwall currently in the New Quay Real Photo set. Happy to give you a link to the cards if it will help.
Hope this makes some sense.