I can’t comment on north Wales - I am a Londoner living in a city on the south coast that isn’t Cardiff (I suspect I’m in the same place as @GoodbyeMrChips ). Much as I love London, I love it here more, and wouldn’t move back for anything. Tried not to be too ‘rose-tinted’ with my post though.
The (massive) positives are that it fits the 15 minute city idea - a proper neighbourhood, great schools, GP and dentist, good range of local shops, gyms and swimming pool, a rapidly developing cycle network throughout the city, 10 mins to stunning beaches (via parks). Have theatres, concert venues, quite a bit of cultural activity. Fantastic sporting facilities too. Loads of activities for the kids that weren’t possible when we were in London are on the doorstep here.
Short drives (~30 mins) to wild beaches and dunes, waterfalls, mountains, forest, marshes. I’m outdoorsy so this is my priority.
V busy and touristy in the summer but doesn’t really bother me - we are all tourists somewhere, and we have the place to ourselves for most of the year.
Shopping is pretty dire but can get to Cardiff (1 hour), Bristol (<2 hours) or London (<3 hours) via a v regular train service. This is enough for me to get my city fix.
Public transport in the city is a bit crap and quite expensive - this would be the main thing I would improve. It does mean that there is a lot of car dependence here at the moment. Also there are issues with drugs and poverty - but not unique to here. Saw similar in London and English south coast.
Welsh language schools are available but these are in addition to catchment schools. Welsh language usually ‘desirable’ at most on JDs - have seen a few jobs with ‘essential’ but these are for posts involving work in Welsh-speaking areas. Not sure why the negativity towards Welsh - it is the national language.