I do believe I've found the case solution: https://elevatorsound.com/product/damaru-x-elevator-sound-eurorack-modular-travel-case-7u-104hp-70mm-deep-black-w-central-1u-rail/ They have this arrangement in 84, 104, and 126 hp widths. I think they'll also pre-fit the power, as they have a "special order" 126 hp version with power installed. Probably best to drop them a line and see what they can do for you. My suggestion would be to go with the 104 hp at this point, unless you've got an expansion direction already sorted out.
Vactrols are cool...what they are is a sealed package that contains an LED and a photoresistor. So when you hit a vactrol with a +5V trigger pulse, it rises almost immediately...but then it tails off slower. Granted, that's "slower" in terms of milliseconds, but it's just right for feeding a trigger into its control point and a noise source through the filter/VCA combo to get a quick little "snap" in the noise color and with the filtering you want. The Tenderfoot module has three different response settings, also...a more "normal" LPF, a "darker" LPF, and VCA only, and when the vactrol tails off in the filter modes, it also rapidly sweeps the filter closed in addition to killing the audio by closing the VCA. Should result in some really neat "snappy" percussives...somewhere halfway between 1980s electro and weird Berlin dub clicks and pops.