recently i've come to know the windows server migration tools cmdlets. i'll put this info here in case it is useful.
note all the microsoft links below are a pain to follow, but they work well. just read carefully.
if you have local groups, and your acl's (ntfs or shares) depend on them, go ahead and use powershell to install the windows server migration tools - ms link 1.
use this procedure - ms link 2 - to move the groups (albeit with a different SID). note you only need the -Group option and not user.
with that, the actual moving of data and shares outlined here - ms link 3 - will work. in my experience, it is very slow. also, if you already had data on that folder, it will not overwrite all share and acl info (even with the force option). so, if you are just starting, do everything from scratch.
although i don't see a "resume" option, it will go a bit faster if it doesn't need to copy anything; but even if it doesn't, it wil take a good time. it is probably not a good idea to try to sync in downtime if you have a lot of shares.
it does not respect directory timestamps, but it does respect file timestamps.
my best try will be using it fully for shares i hadn't already started copying, then using the "share only" option on those i had copied, and use robocopy; i will have to double check a lot of permissions manually because robocopy checks SIDs literally. then when performing a cutover, mirror only data, but not the acl's. i'm still debating :) i read an old article that can modify SIDs that is actually looking like less work.
if you don't have local groups, bless you, use robocopy and re-create the shares with the "shares only" option. or even recreate the shares manually, you have an easy one :)