Today I upgraded to the Master Tier subscription and when I use the character creation tool I see that I do not have access to content outside of the free package. When I go onto my subscription manage page, I can see on the top banner that is says to sign in or register which I find weird. But whenever I go to create a character I still only have access to the free content, I know this because I am in my friend's campaign where they have content sharing on, and I have access to additional content.

When I go to create my character I select all the options for source content to use (besides partner content) and still, I only have access to the free content.

Subscriptions do not control access to content from books, those are done via separate one-time purchases. Subscriptions only control things like how many characters you can create, and the ability to turn on content sharing. Content sharing is done at the campaign level, which is why it works in that campaign where your friend has turned on content sharing. You can, however, theoretically make more characters in that campaign and move them out, and they'll keep the content you added to them while in that campaign. You just won't be able to add it back again.