Racks always seem to be an afterthought for many, as mentioned it should be seen as a critical part of the whole sound scape as would be the room.
There are plenty of hifi racks that follow two basic theories 1) to isolate vibrations and resonances to each component and 2) to couple components to the rack and to dissipate and discharge vibrations and resonances into ground/floor.
In addition there are many gadgets that will offer some form of either, ie: Stillpoints, Aurios (ball bearing isolation) springs and or air cushion devices, to the coupling items like spikes and discs.
Either one can be beneficial especially for turntables and bass speakers, but all components can benefit, there is plenty of discussion of what method may best suit, but your setup and room may well dictate what works for you.
My advice is to research and see what makes sense to you and if possible experiment, my word of caution decide on one method or the other trying to use both methods counteracts what you hope to achieve and likely lead to complex issues that are near impossible to figure out.

Home Theater: LG 4K C7, HD621, G61RSL, Oppo 203, MS600, DSP3100 L & R, 2x3100's centers and 4xDSP3100's surrounds. 2x REL S3 SHO and 2x REL habitat1 subwoofers.
Music & TV: Sony 4k XBR 65", Oppo 203, HD621, G68D, C15, 588, M10, M20's, M33's, 4xDSP33's
MD600, 2xTwinStores.. 2xMS600, F80, Prime headphone and PSU.