You can use your judgement there! Include headcanon that might make a difference, mostly, as a rule of thumb. But if you don't have a lot of huge events that you're using pre-canon, you don't need to get into a lot of detail, either. For example, on an app I did, I just wrote a few short paragraphs outlining some basics about his life pre-canon that weren't on the wiki. I didn't bother getting into a lot of details, because not a lot of it is needed, either. If that makes sense?