When it was confirmed that Dragon Age: The Veilguard was mostly doing away with world states, many started to worry that this meant BioWare was setting up its own canon, ignoring player decisions. The devs were quick to assure fans that this isn't the case and suggested that certain topics would be avoided so they didn't contradict our playthroughs.
Spoilers for all four Dragon Age games ahead.Now that Dragon Age: The Veilguard is out, we can see that this is, for the most part, quite accurate. None of the larger decisions - like who's sitting on the throne in Ferelden and Orlais, or who's leading the Chantry - are canonised. However, some smaller decisions are, and most of them involve erasing the bad endings which characters could receive as a result of our actions.
I noticed this most of all with one of the conversations that Rook has with Harding, in which you can ask her about her time with the Inquisition. Here, she avoids mentioning things like whether or not you sided with the mages or Templars, but she does establish a few details which might not apply to every game.
For starters, Sera and Blackwall were recruited, since...