I seem to be asking rather a lot of questions lately. I hope that you don’t mind.
I started wondering about regional differences when, SSIW lessons introduced the Conditional “would” earlier on in the Northern course. I wasn’t sure what I was hearing because it sounded so much like the future tense so I had a look at Tony Ellis’s book “Y Cyfeiriadur”.
Ellis uses (p182) mi faswn i, mi faset ti, mi fasai fo/hi etc as part of BOD, to mean “would (do something)” or “would( be something)”. He adds that, in speech, the “fa” is often omitted eg “ ’swn i’n licio”.
Further uses of the tense are given as:
“Faswn i wedi….” to mean “I would have….” and,
“Fasai ‘n well gen i…” to mean “I would prefer…” and,
“Fasai rhaid i mi…” to mean “I would have to…”.
In conclusion – and this is what really struck me – he says,
“In writing (and in speech in the South) the stem “bydd-“ is used in place of “bas-“. This looks rather similar to the future tense (“bydd”). Be glad that you live in the North!”
Y Chwiliadur Iaith” (by Non ap Emlyn similarly opts for baswn i, baset ti etc.
Non ap Emlyn (p38) also opts for ddaru mi, ddaru chi for use with the past tense in North Wales assigning use of wnes i for use in South Wales and parts of North Wales.
When in Wales, i spend most of my time in and around Blaenau Ffestiniog. How likely are such variations to matter?
Questions are good - thank you for asking them 
Not. At. All.
Whatever you say, you’re going to be understood - and if by any chance you’re not, it’ll probably only mean you need to repeat a little more clearly. I’d be surprised if you actually needed to try and find a different way of saying it more than once in a hundred times…
Once you’ve really got your ears tuned in, you’ll probably find extra different ways of saying plenty of things up in Blaenau… 
It’s always good to ask questions!
As far as I’m concerned, the more the better - just don’t wait until you get an answer to carry on with the lessons, listening to and speaking Welsh whenever you can in the meantime!
Yes, there are a few “stems” of the verb “to be” in use for the conditional.
Just remember that no stem is past, present or future in itself- it depends on the ending given to it, so no stem is going to sound like the future on its own, as it were! Most stems stay the same for every tense- past, future and conditional, so having the same stem for future and conditional is quite normal!
What, “matter” as in one or the other forms won’t be understood?
Not at all.
“Matter” as in “now you know about these other forms, you won’t be as thrown when you hear them used, and may be more prepared to use them if you find everyone around you using them?” - well, that could matter, in a good way!
So, basically, no one will blink an eye at you using any of those conditional forms anywhere!
Oops! Aran posted while I was writing! Best answer from him as always. Would delete answer but that leaves a mysterious message which leaves everyone wondering what was in the one you originally posted…
No, don’t! You go into detail that I didn’t touch on (no surprises there, from one of our most supportive grammar hounds…;-)) and your post is a valuable addition to my quick response 