Which filesystem should I use in an SD card on a NAS?
Here is the info I was able to find online.
https://en.wikipedia.org/wiki/Flash_file_system#Linux_flash_filesystems mentions JFFS, JFFS2, YAFFS, UBIFS, LogFS, F2FS. Some of these (but not F2FS) are targeted for raw flash devices, F2FS is targeted for flash-based storage devices which already have a translation layer, such as SD cards.
I've found this 2011 question useful about the filesystems available back then: https://superuser.com/questions/248078/choice-of-filesystem-for-gnu-linux-on-an-sd-card
https://developer.ridgerun.com/wiki/index.php/High_performance_SD_card_tuning_using_the_EXT4_file_system mentions ext4 mount flags
-o noatime,data=writeback and explains how to create such an ext4 filesystem. It also recommends some cache settings in
/proc/sys/vm for increased performance.
https://wiki.gentoo.org/wiki/SDCard#Filesystem mentions some ext4 performance tuning settings which specify block sizes.