Can I safely delete the migrate tables after migration?
Yes. If you're doing a "one-and-done" migration you can remove the tables. Just make sure to:


uninstall the migration modules
remove your relevant migration config
then remove your DB tables once you have no code/config dependant on these tables.


Note, the caveat is you're wiping out your migration history.

The migration framework has an ongoing issue about this topic. These tables are persisted since these they capture migration source/destination metadata. The metadata is important if you have a phased, or ongoing, migration. If your migration project is over, the metadata has no relevance.