there is no ‘instant-pad-mute’ on the EP-133, main reasoning behind this is to avoid scenarios where you’re like, "why is this thing silent… so the way/workaround to do it would be to us amp (level) which is per pad.
select pad (you can do this with shift + pad) -> [sound] -> x-knob -> dial down amp to 0
about filter per sample, doable but would be cpu-bound, i.e. would eat voices. ps. the cpu is an ARM M4+ running at 150MHz.