Bore da all! Myself and my immediate family are planning a trip to North Wales later this year if COVID allows. I am from the South and learning the South Wales dialect, I thought that going up would give an ideal opportunity to get some practice in but I’m hearing about “significant differences” would people not be able to understand me at all in the North?
Don’t worry, they would recognise that you’re speaking Southern Welsh but that doesn’t mean they wouldn’t be able to understand you - the ‘significant differences’ really only occur in a few constructions, and even then although it might throw some ‘Gogs’ for a few seconds, it’s really not a barrier at all.
You’ll be fine. TV and Radio Cymru has helped familiarise people will all the different varieties of Welsh.
I’ve learned the South Walian version, and live here. When I speak Welsh, even here, to a first laguage speaker, I’m often asked if I’m a Gog, a northener. It’s Welsh, but not exactly as we know it. If people claim they don’t understand you, they are being very picky! You’ll be fine. You might even come across @aran and @CatrinLliarJones.