As someone with friends and family on the spectrum, my best tip:
Take a moment to breathe when you've completed a thought related to what you're explaining, and look at the other person to see if they have information to share, questions, or just to express what they know.
This helped a few folks pace themselves, and the break for others they believe helped in not appearing condescending.
Hope this helps!
TONS.
My local library is about half for under 12, a quarter or the space for teens, and then the last quarter is a split of nonfiction and fiction for adults.
So if you go as an adult without a plan or a request that came in, you may not find much other than the librarians latest rec or the newest additions rack.
For kids though, my local library is incredible. Reading nooks, educational play areas for the little ones, etc. Its wonderful.
My oldest is getting anywhere from 6-8 books a week right now, she's going into 2nd grade. Libraries are awesome.