Just jumping in here.

The Rockpi4B that I got came with 32GB of  EMMC memory, not all suppliers include it so worth checking.

I did a benchmark using gnome-disks. on my Rockpi4B and compared using an SD card or even a M.2 MVNE memory module.

The differences speak for themselves.

This is a simple read test and the average speeds achieved I will let the numbers speak for themselves!
SD Card.     ~  20 MB/sec
EMMC.        ~ 160 MB/sec
M.2 NVME  ~1500 MB/sec

To be fair the write speed average is much lower for the M.2 NVME and very similar to the EMMC. at 160 MB/sec.

The SD card write speed is still around 20 MB/sec.

The RockPi flies and blows the Raspberry Pi out of the water, but there is a very small user base out there so take care.

Just wish I could get my Toupcam to work with it.