An excellent question, so I did a quick Act 1 runthrough with an Awakenings-only character I had.
As soon as I tried, it told me my character's history was incomplete, and that it will fill in any missing decisions from a preset history.
I just did a quick whizz round Act 1, but this is what I noticed:
- The ambushers outside Lierenne's said 'Long Live King Alistair' when I reassured them I was Ferelden.
- There was the Dalish assassin confronting the former werewolf on the Wounded Coast
- The Harrowmonts did not appear in the Docks
- I triggered The Conspirators instead of Secret Rendevouz. However, this is in keeping with the decisions I made as my character in Awakening.
In conclusion, it looks like the game does indeed record your Awakenings choices, and fills in the gaps with the decisions taken from the Hero of Ferelden preset (Connor lives, Mages recruited, Dalish recruited, Harrowmont throned, Caradin supported, Ashes disappeared, Dark Ritual accepted, Loghain dies, Warden kills Archdemon, Alistair rules alone, Zevran lives, no DLC choices flagged).