Im womdering if i can use this or something else just to copy user data (ie emails, accounts etc) but nothing else. I can move accross the mariadb data and files after. Might be a cleaner way of doing it then i wont be in a position that i copy some wierd old settings over?
James you really need to reed the Wiki.
https://wiki.koozali.org/Migratehelper#DescriptionMigratehelper will:
Make a back up of all your configs and settings but NOT your data files in ibays or emails. It does include DBs. It makes it much smaller and faster.
You can use this minimal/small tgz to restore to a new server, and then SCP the emalis and files across the network. Exactly as described in the wiki.
Your big issue is migrating from 9 - 11 which you can't easily without risking a lot of trouble - you'll really need to get to 10 first and check everything is OK, and then do it again to 11. Note you may well have issues with ssh and ciphers - there are solutions around here.
You really need a test machine to trial this first.
Otherwise just do a USB backup/restore v9-v10 and v10-v11