I like to use /(root) as read-only partitions in ext4 (for example). I like to use /var/log, /tmp and /run such as tmpfs and another partition for rw.
If FlashNAND, you can use UbiFS, SquashFS (also in eMMC, but read-only) but ext4 in the latest tests on embedded I saw did very well.
It is important to remember that eMMC has already internally wear-leveling, and reducing the wear of the blocks, as in a NAND flash you must implement and use BAT and other techniques to help.
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