in terms of durability and fewer repairs, which Macs are the best and worst?

I don't think Apple publishes those numbers. Most generations have some design changes in the case and motherboard. Any design weaknesses in one generation likely won't appear in the next.

Any model with only integrated graphics will likely be more reliable. They have fewer components which can fail. The odds are in their favor.

The MacBook Air should not be considered. It is quite old. As I understand it. The Air is just a legacy model now and will simply fade away. It's name is a bit ironic as it weighs more than a Macbook.