So I searched the forums and got a an answer to some extent, however it did raise a few other questions for me as well.
So I understand that you pick one (1) archtype at 1st level and go from there (getting all the benefits from that class as you progress).
However, you can also dip into other archtypes as well and receive benefits from them for their respective levels.
However, I`m a little confused about how you would work some of these archtyping mixing classes:
1) do you take your archtype at level 1 and then level separate archtypes the same way that you would if you were multiclassing?
2) So long as there are no conflicting features, you are capable of taking an archtype in the same base class? As well do you just make sure that the conflicts at level 1 are ok (should you only take 1 level in an archtype) or do you have to make sure that there are no conflicts from level 1 onwards?
As an example I'll use Musket Master Gunslinger and Mysterious Stranger Gunslinger. Nothing within those two archtypes conflict (in that they both give up features, but they do not give up the same). I pick my archtype as Musket Master and choose to level 1-19 as that archtype. However, I make the decision at level 2 to invest one level in Mysterious Stranger in order to pick up the ability to use CHA as my prime stat. I am now effectively (at level 20) Musket Master 19, Mysterious Stranger 1. I use CHA as my main stat, maintain nimble and gun training skill and all the other features of Musket Master.
Does this sound right, or is it because of the fact that at level 5 in both archtypes they replace Gun Training, I am only allowed to take one or other (despite the fact that I'm only taking one level of Mysterious Stranger)?
1: All the archetypes modify the same class. There's no multiclassing when choosing multiple archetypes. All archetypes should be chosen at level 1, but many DM's would allow you to choose an archetype later if you haven't used the abilities the archetype replaces.
2: The archetypes you choose can't conflict at all, either on future levels, or even on levels you have no intention of reaching (for instance, if the campaign is going to end while the PC's are 10th level, you still can't choose archetypes that have conflicting 15th-level abilities).
You can only take multiple archtypes if they don't replace an identical ability at any level, you don't have to make the choice at 1st unless an ability is replaced at that level.
Archtypes aren't classes, they swap class abilities for other abilities. You cannot "just take" 1 level of mysterious stranger. You cannot take both archtypes because they both replace the same ability.