Keyboard is the same but you have a lot more space to stretch out and rest your palms for larger hands. I’m cramped in 15” and 13” is totally unusable.

Yes. All sizes, even 11" air, had the same keyboard. The touch pad might have been bigger.

No, the 11” Air had a smaller keyboard: just look at the function keys on it.

The 11" Air keyboard is the same width, but not quite as deep.