Jen....you are totally over-thinking this
Take you time and get to feel comfortable here...I promise, you'll fit right in!
As for mixing and matching colors, themes, etc....I have seen albums that matched and some that don't....I love it both ways.
One thing about mismatched, if they are all mismatched, that kind of makes it a theme of a sort...KWIM?
I've done matched up 2-page color schemes but if they are not completely, it was ok. I tried to at least match up by color vibrancy or warm/cool tones and subject.
I don't think there is a right or wrong answer on this. It's whatever you want to do.