Maybe you'd want to make the emuNAND partition first?
it'll create your emuNAND by extracting/copying your current firmware (9.x) so you won't have to update it.
no game uses 10.x for the moment.
and all already installed games will still work and be present.
if you downgrade now, you'll lose everything you did since the backup, and you'll create your emuNAND based on that clean NAND too.
up to you, but think well and logically before doing anything.