Board pop is when you step on the tail and it "ollies" up out of the water. Kind of like the board is creating it's own ramp with the bottom shape. Some boards are worthless at this, but can be great at handling chop specifically because they don't send you up off of every piece of chop or jump up every time you over weight the tail. Boards with less 'pop' make great beginner boards because they don't beat around the rider so much when they are still trying to figure out board control.
"Load and pop" is when you combine the kite tension via a quick direction change upwind, and press the tail, to combine the most powerful aspects of each -
1. changing the wind-window by moving upwind (puts the kite further back in the apparent wind window and increases the wind speed throughout the jump)
2. Tensioning the lines with the upwind movement (kind of part of number one, but helpful to think of it as separate)
3. Using the 'pop' of the board to initiate some upward movement, and breaking free of the water's surface (in chop you can use a ramp, but in flatwater, you have to rely on the board's "pop" to break free of the water's surface without using some of the kite's power to do it - you use forward momentum to break free so the kite only has to lift you)
Just a note: I have used lots of TT's with varying degrees of "board pop". But the board with the most pop I have ever ridden was not a TT, it was a directional - the 2012 North "Whip" quad finned kitesurfboard. Just put a bit of weight on the tail, and it would come off the water. Other directionals I have used mostly had less board pop than TT's with the most pop. However, "load and pop" is typically superior on a TT because of how hard you can sink the edge (edging) against the wind for a more powerful, and quick, turn upwind. Surfboards, even with their larger fins, just don't bite so well as you lose forward speed (fins need fast water flow) carving going into the wind on the setup.