"I am going to play squash."
Translation:Dw i'n mynd i chwarae sboncen.
As I understand it, rydw is the form of the word in the standardised form of Welsh known as Cymraeg Byw. I believe it's not part of the traditional spoken language in any part of Wales, while dw is one of those forms used by native speakers.
So rydw is correct in writing and you'll hear it from learners while dw is arguably more authentic.
Hmm, that's interesting, always assumed people would be more informal when speaking than typing, but it makes sense that rydw is used for more formal things. I've seen ydw used in the emphatic, now I've checked my old notes, but rydw definitely feels wrong there.
Thanks for the insight!