Update on the update!
Big difference running coreelec from internal flash. The UI is very snappy (now I finally feel the difference to my old raspberry 3/microsd setup) and opening/loading things happens much faster.
The system boot is also much faster.
And using ceemmc was a ease. Very fast and it gave already a sneak preview of the internal flash write speeds:
Copy all data from '/flash' to '/media/CE_FLASH'
222.89M 100% 20.54MB/s 0:00:10 (xfr#68, to-chk=0/79)
Syncthing, please wait...
Copy all data from '/storage' to '/media/CE_STORAGE/coreelec_storage'
482.59M 99% 34.98MB/s 0:00:13 (xfr#1018, to-chk=0/1430)
Quite impressive that in all it took only 23 seconds to copy the system from usb to internal eMMC. Not sure if even the read speed from usb2 stick bottlenecked it.
Any how I’m very happy now and can only suggest:
INSTALL CE ON INTERNAL FLASH NOW! (if not already happend 
)