I have few questions related to AIP migration to MIP:
How will the metadata on the file change when organizations migrate from AIP to unified labeling? On old files & new files?
What happens to labels with non-unique sub-labels between parent labels - ie (restricted/HR & Unrestricted/HR) which is allowed with AIP and not with MIP? Will the labels change
Will the label GUIDs change when migrating labels from AIP to MIP?
Existing metadata should not change, you should be able to see these same fields in the advanced properties of your office files as an example.
If you have independent sublabels under two different parent labels you shouldn't have a problem in migrating that over.
GUIDs do not change.