Can someone explain the possibilities of trade vs release for the guys most likely to be rid of this offseason? In terms of cap room, trade value, etc.
In nearly every case, traded players are handled just like released players from a cap standpoint. An exception would be if you were able to trade a player to which you still owed guaranteed money in the future and the new team was willing to pick up that obligation. That almost never happens though.
It usually just comes down to the player's value. Consider also that the other teams around the league know who is in danger of being cut, so rather than trade and give up something, they will often just wait for the player to be released and take their chances they can sign them. When trades do occur with players likely to be released, the new team is only gaining exclusive rights to the player and keeping them off the open market, so they usually don't want to give up much in return. Case in point is Asante Samuel. He's a good player, but all Philly got was a 7th round pick from Atlanta.
Guys like Gamble, Gross, DWill and some others are potentially tradeable, but we'll get a lot less for them than we'd like. It really only is worth it if we plan to cut them anyway.