First, two videos to give an idea of the overall process:
1) During the building of the RPI 4 (8 GB version) case process, I did not screw in the bottom section to complete the case. Rather on the bottom half of the case, I combined the small 'A' plug to 'A' plug USB adapter (which comes with the Argon One case kit) with an 'A' plug to 'A' socket extension cable to bring out the USB connection.
2) I downloaded the latest stable versions of LibreELEC (9.2.6) and RaspberryOS.
3) I flashed the RaspberryOS onto a fresh SD card. I flashed LibreELEC onto the SATA M.2 SSD using the extension cable plugged into my desktop.
4) Using only the top half of the Argon One case (with the RPI4 & daughter board secured), I installed the SD card, connected power, HDMI to monitor, USB keyboard & mouse, network cable and booted the RPI 4. The M.2 SSD was not connected to the RPI 4.
5) Following the instructions in the video, I upgraded the RPI 4 firmware (version 000138a1 or greater). Once finished, I powered down the RPI 4 and un-cabled it. I removed the SD card, finished assembling the Argon One case and added the small 'A' plug to 'A' plug adapter as per the videos. The new assembly was cabled with power (turned off), HDMI, Mouse and KB. No network or external storage connected!
6) Turning on the RPI, I watched on the monitor that the system attempted to boot from the missing SD card multiple times. Then suddenly (like magic) the RPI booted up LibreELEC OS from the SSD M.2 drive. I added the network cable, external USB storage and finished configuring LibreELEC.
The older RPI4 running LibreELEC on SD card: videos from the external SSD would halt several times before playing properly. Streaming videos were exhibiting the same halting issue.
The new RPI4 running LibreELEC on the M.2 SSD: videos (from the same external SSD) now play as if they were on a BluRay/DVD player. No halting, virtually no lag. I still have to try out streaming services like Amazon or Netflix, however, I do not anticipate any streaming issues from Kodi / LibreELEC / RPI4 hardware.