Dragon Ball, DB Z, DB GT/Canon?
I've seen in some of your answers you said movies and other Toei-only things are "non-canon". But when it comes to DB, does that really mean anything? There hasn't been anyone official saying what or what isn't to be considered "canon". Everything just is. If it just means "it's not in the manga", what would be the point of saying it's "non-canon" when discussing about Broly (for example)? If he's not canon to the manga story, fine, it doesn't matter, Broly still exists and has a story, and the original story is "canon" to it.
It seems to be a pointless concept, and it's subjective at best. Most fans misuse the word to refer to continuity, or what they accept as part of the story based on preference.
You make a very good point in mentioning how there really is no official declaration as to what is 100% canon and what isn't. Though that's not entirely true, I'll dissect the topic.
I've always seen two types of canon material, manga and anime canon. So for example, the Garlic Jr. Saga and DBGT. Yes, I would definitely say they are canon to the anime storyline. Nobody can really argue that. The same goes for all of the filler episodes, such as when Gohan met a bunch of orphans, and many many many other episodes. They are not exactly canon to the manga, however it is part of the anime and therefore canon material.
That said, the aforementioned material is physically possible to be fit in to the canon storyline of the manga, unlike the movies which can only be explained as being in an alternate universe. I could do this for every single movie, but take Broly for example. Goku and Gohan should have been Super Saiyan the entire movie because Gohan had short hair. (It was cut inside the Time Chamber and when they came out they were Mastered Super Saiyans). It can also be argued that the Z-Warriors wouldn't have been on a picnic when it should have been within days before the Cell Games. Along with Goku being with Chi-chi at a prep school, it was made with the atmosphere that Earth was under no immediate danger from Cell at the time of the movie. Truth is, the movies are non-canon material made for the enjoyment of fans because the franchise itself was so popular. Spin-offs. Broly exists of course, and he and all the movie characters have a story, but the original story most certainly is not canon to them.
I think that non-canon is a word that must be used to make sense of many things, but I do however truly wish that it didn't have to be used so often.
As you know, canon material is material that relates directly to Toriyama's manga. So basically all of the movies couldn't be classified as anything more than non-canon. Filler material (Garlic Jr., GT, etc.) can be counted as canon material, but I just prefer to consider it anime canon material. The first DBZ movie can be put in that category as well because it correlates directly with the anime despite the fact it still has a contradiction in it. (Krillin meeting Gohan, and then not knowing who he was in the actual anime on Roshi's island).
As for all the other movies, yes they do exist and have their own story, just like how video games exist and have their own what-if stories. But if you try to fit them in to the canon storyline, you get a mess.
Side-note, the 14th DBZ movie coming out next year is actually going to be canon to the main story. It will be the first Movie that Toriyama himself will actually do work on.
Thanks for the great question!