Don't know where you are. If in a cold zone, mulching now will help protect the roots of the new plants over winter.

yes, 5a. I kind of thought that, but just wanted to know what others thought.

Yes, add mulch now as it will keep the ground warmer giving the roots more time to establish before the ground freezes.

Yes. It's also easier to walk around the beds now, when the soil is drier than it will be in the spring. Plus you'll be ahead of the emergence of spring weeds and dandelion seeds lofting around. Mulch certainly helps to control weeds.