I'm designing a simple triac chopper circuit for use as an AC motor speed controller. The input is 120 VAC and the load will draw 1 A or less. I want to include an LC filter on the input side for RFI suppression and an RC snubber for the inductive load. I'd like to get some advice on selecting the proper type (not value) of capacitors to use in each portion of the circuit.
I've attached a generic schematic below. It's essentially the same as a common lamp dimmer circuit. L1/C1 is the input suppressor, C2/C3 are the triac trigger caps, and R3/C4 is the snubber.
I know that C1 should be X2-rated because it's across the line, but I'm less sure about C2, C3, and C4. These caps should probably be film/foil to handle the surges from operating the triac, but is an X/Y class rating necessary? I recognize that the safety classes only describe the failure mode, not the use case, but they're still technically an across-the-line application even though the caps are in series with resistors and other components. Does it really matter whether they fail short (X) or open (Y)? I've also read that safety capacitors are intended for line suppression and aren't really designed for snubber circuits and whatnot.
I took apart a commercial lamp dimmer and found a circuit similar to the one I'm building. The equivalent of C1 is a boxed film cap (no safety rating from what I could tell) and C2/C3 are dipped film/foil, but who knows the composition. Just looking for some guidance on best practices... I'd appreciate any input.

