thanks for answering.
i have reinstalled majaro with the help of calamares not too long ago, so except for /home, all partitions have been adjusted before and offer these extra flags already.
my cpu supports sse 4.2, though i have not yet added crc32c_intel hook to GRUB_CMDLINE_LINUX_DEFAULT.
the question that bothers me: is it recommended to apply these changes to an existing filesystem - or perhaps is it recommended at all?
the second link even states it is currently(?) impossible to do so? having 64bit metadata_csum support to me, seems a good thing to have - but i could also imagine that it will slow down things?
or, to work around this, better consider booting into manjaro-live, reformat /home with kdeparted, than install grsync and sync my backup to new /home in live-mode? probably fstab and permissions would have to be altered accordingly to my previous installation though...
so many choices, i just thought i share this with you guys and girls and see what you think about it, well that's it