I need help understanding professions.

I've been looking at guides for Legion and I'm confused about it. I have a few questions.

1.) Some say that it's not important to have professions maxed before Legion. Is this true? If it is, why?

2.) I saw also that I only need my professions level to 300 for the profession quests. Does this mean I'll be able to gather ore/herbs/etc. in Legion even if my professions aren't maxed?

2.1) An extension of the question above, will I be able to craft recipes from Legion without my professions maxed?

Sorry if these are noob questions.