Request for best practice overlay (root/data/...)

Installing and Using OpenWrt
#1

I am still lost in the best practice for my espressobin between overlay_root overlay_data or root partition fullsize...

I have 4Gb on uSD or in eMMC.

I still use the ramdisk for the first installation.
The soon to come 19.07 works really fine, in self compilation or in the snapshot branch.

Is there any experiences, long time tests, with upgrade case take in care, for the subject of overlaying ?

Thanks in advance

#2

For reference : SysUpgrade with extroot overlay

#3

UP again, what about the best recommendations of rootfs_data /overlay with a ext4 sdcard image from snapshot ?