Question about Auction Style Dynasty rules

I know auction drafts are a thing. And dynasty is a thing. I believe the draft guide will even let me sort by dynasty and auction format.

If these leagues exist I am curious to see how folks handle the dropping of players who are under contract to the team but not retired from the nfl. (To create cap space for signing new free agents.) What is most typical?

Also I am curious how these teams handle rookies. A rookie auction? A rookie draft?

I don’t need full league bylaws, but I guess if they answer the questions I won’t turn them down. Thanks.