How to boot with initramfs on Raspberry Pi 4

What I want to do is:

How to boot to USB RAID - Raspberry Pi Forums

Any other guide to jump boot process to USB and to that be a RAID of pendrives?

My final goal is to solve this:

(Rpi4) Crackling sound when video has HD resolution

With Raspbian (Kodi18), a USB RAID really helped on HD media playing, but I’m trying now to migrate to OSMC (Kodi19) and reach same performance.