Welcome to the hub for all side missions in Splinter Cell: Blacklist. Some videos have commentary, others are pretty easy to follow. Definitely complete the Grim 4E missions first, simply because it will make all other missions undeniably easier to maneuver with the stealth suit she unlocks for you.
These missions periodically unlock components for the highest tier stealth suit (recommended finishing these before attempting Ghost Perfectionist Campaign. You can follow that walkthrough here.)
These missions periodically unlock new Black Market weapons for Kobin to sell to you (Recommended before starting an Assault or Panther playthrough). These missions unlock after completion of the Safehouse campaign mission.
These missions periodically unlock components for the highest tier armored suit in the game (Recommended before starting an assault playthrough).
These missions periodically unlock components for an exclusive Voron suit (Voron is the enemy that you face in the exclusively co-operative campaign alongside Briggs).