The usual I've heard was 1 nest per 3-5 birds.
I have 4 and have had up to 20 birds, I have 13 now.
There' is occasionally a traffic jam or some squabbling, but it's worked out fine..
Maybe.
How many birds will you have, in how big a coop?
Here's my thoughts about heights:
https://www.backyardchickens.com/articles/coop-stack-up-how-high-stuff-works-well.73427/
I have poop boards too.
Both the boards and the floor are covered with heavy duty foam backed vinyl sheet flooring. It wasn't cheap, but I bartered for parts of the cost, and it's held up well for 10 years now.