The breach charge set at the very beginning saves about 1 second compared to waiting to activate sniper support to get the uzi guy when he enters.

The 4 slow motion rooms are set up in a line from top left, bottom left, top right, bottom right. Each right side rooms and the bottom left room can have a hostage instead of an enemy (great for high score, bad for speed runs). The top left room left side enemy can also be a hostage, but the enemy and hostage on the right are static. By going to the top right room first, sniper support can potentially clear either the bottom left or bottom right room entirely. Ideally the bottom right room because it saves time walking.