From our understanding, we thought soldered eMMC is better for commercial customers since it will reduce the issue of eMMC module installation.
For installation, ROCK Pi X is always USB to eMMC. If you want to deploy a lot of devices, you can always generate a custom OS image on another PC and dd it to eMMC when booting from USB. Since it’s UEFI boot, basically you only need two partitions, one boot partition for .efi utilities, the other for rootfs. You can always chroot and pre-configure the “master image” before deployment.