I would just always default to resistance as my cantrip and enjoy +2.5 to most of my saving throws, with the possibility to giving the bonus to someone else, situation demanding. That is one hell of a cantrip.
Overall, I really like these changes. Dragonborn will be more likely to actually use their breath weapon, and the flight only comes in at level 5, when it is more balanced, and has limitations so it isn't too much. I think they really hit the sweet spot with this race.
Goliaths were a fairly popular but basic class. Now they are a little more interesting but there might be some balance issues: if you are a martial class the hill giant ancestry that lets you automatically knock an opponent prone after a hit is going to make them the go-to choice for martial classes, tanking builds in particular.
Ardlings are...fine. Generic option for folks who want to play an animal-person that isn't Tabaxi, Kenku, Tortle, Harengon, etc. In terms of story, I would much rather they were the result of experimentation, like a Dr. Moreau situation, than the divine origins thing.