1. Im not sure, but i think:
- You can resign all Bird exceptions in the game to exceed your cap.
- You can use the mid-level exception to exceed your cap with as many players you like unless the salary of all of them together is under the mid-level exception. In general you just want to have ONE good player instead of a couple ones with low salaries.
- You can sign as many players with minimum salary contract to exceed your cap.
2. There's no difference except that you lower the cap for the other team in the processing season.
3. Well they count against the cap, but you can draft the rookies even though your cap is already full.
I'm not sure with my answers. But i think the game works like this.
So it could sometimes be wisely to sign first the players who are not in any exceptions. When you are having your cap full, you can exceed your cap with all the exceptions. The only risk is that some other teams may take your star "bird" players under contract before you.