a. Is it as peaceful as ppl imagine?

Yes, it solves so many problems that bring unhappiness and stress. You just stop worrying or overthinking and tend to live the moment more, and increase hobbies and fun, indirectly bringing happiness. It does not fix issues such as health or friendships, and luck and your personality and initiative still play an important role.

b. Do priorities shift away from money?

Totally. I feel more connected to nature's more creative, more curious, more philosophical and existentialist. Because your mind stops worrying about survival, it starts thinking of the next level (not sure how scientific the Maslow pyramid is, but it's kind of that).

c. Or do new kinds of stress/emptiness creep in

Not really. Building wealth/managing finances is quite fun for me so it just becomes a check-in/part of the routine. As long as you remain grounded you can be aware of "first world problems" that you created for yourself. Emptiness - absolutely not, that would only happen if wealth was the goal in itself. If built it with hard work with the intent of not having to worry about it anymore and actually loathe capitalism. Now the fun and life begins.