1 point2nd question Inside the task sequence, there is an "Join Domain or Workgroup" option where you can have the device join a domain. I have never used it separately from imaging but I don't see why it wouldn't work for what you want to do. I would try to have it perform the backup, restore, then add to the new domain. keep in mind you have to have an account on the new domain so SCCM will have rights to add the device.
1 point1st question - we have two separate task sequence. 1st at 6pm disable bitlocker restart computer request state store capture user state re-enable bitlocker 2nd at 2am request restore state restore "customize how it's restored" "we have custom .xml files" Lastly, in the Assets and Compliance section, you will see the "User State Migration" section. That is how you associate the FROM computer and the TO computer. Associate the computers / users and let the tasks run