After the draft, some players have the option to "cut" and others have the option to "void contract". What's the difference and why is there a difference?

The void contract will disappear at some stage (don't know when, when pre-season starts??) and means you can just release that player without any cap hit.
With Rookies you can still do the same thing, not so sure about non-rookies though.

I believe the Void option is only for just drafted rookies, and it disappears once training camp begins. This saves you from taking the cap hit for a player you drafted but don't want, like if the AI drafted the player or they are a late rounder you know won't make the team.

If you want to wait to see how they progress during training camp, you'll have to take the cap hit if you cut them after.

I checked and it is the rookies that have the "void contract" option. Thanks guys!