[wrxtasy]

In terms of Kodi speed it is like this so far as storage is concerned:

SSD > HDD > eMMC > NAND > SD card

All R/W is contained on the SD card itself, unless you actually tell LibreELEC to flash to internal, faster eMMC Storage.

Write / Storage operations are noticeably slower with SD cards - but LibreELEC Kodi does not do a lot Write operations anyway day to day.
Its all very usable.