SSiW teaches Ta beth (whatever), ta pwy (whoever), ta pryd (whenever) and so on. However I usually hear people saying Beth bynnag (whatever), pwy bynnag (whoever) pryd bynnag (whenever).
I live in the South East so I was wondering if this is a regional difference or…
Without listening to the challenge(s) to check the the context of them, I’d say the 'bynnag’s are the proper way of saying those. ‘ta’ comes from ynteu which means ‘or’, so “ta beth” is more “or what” (e.g. wyt ti’n dod ta beth? are you coming or what?), ta pwy - or who (e.g. nest ti neud hyn ta pwy?) did you do this or who?), ta pryd - or when (e.g. wyt ti’n mynd rwan ta pryd? are you going now or when?).
I can’t recall which challenge it first appeared in, but Iestyn says that Ta Beth, means either “whatever” or “anyway”
I’ve heard it used for ‘anyway’ on occasion, and I think in some contexts it could be ‘whatever’, so maybe it’s more commonly used for those in Southern dialect than up here in the North. A dictionary would give you the ‘bynnag’ forms though, so it’s definitely colloquial.
Gareth King says that ta beth/ta waeth both mean anyway, in any case or whatever, and that they are very similar to beth bynnag
(p.145, Working Welsh)