I'll take a 'back seat' on the spec part, and on what I feel is Greg's expertise.
I can't visualize using a SPD across the buss that would create a dead short to trip a 100 or 200 amp main. My gut leans toward the dry contacts and the shunt trip main, IF that's what the client wants.
SPD/TVSS don't "stop" transients, they work through voltage drop. The more current that's flowing through the wire, the greater the voltage drop, and the smaller the voltages experienced by the circuit(s) the SPD is protecting. Consequently, fault currents can be pretty high when they activate, 20kA or more. Plenty to trip a 200A breaker if the surge is that high. You want redundancy, you want SPD on the main panel, on the sub panels, and on power strips at the equipment. Damage from transients is pretty rare when the protections are designed right.
And yeah, 20kA+ is a LOT of current for a small device. The MOVs inside them can be damaged by high energy transients. Some of the really high end SPD include monitoring and will work through many small events or a few large ones and tell you when they're degraded and need to be replaced.
