Migrating Nintex Forms / Workflows in Essentials as part of 2.7 build
Known Issues as part of the release notes of 2.7 Essentials
Nintex Forms/Workflow app should be installed before a list/library migration.
Copy Nintex Forms is supported only as part of “Copy Site as Existing Site” because Nintex Forms app should be installed before site migration. Installation of O365 App at "Copy Site as new Site" or "Promote to New Site collection" is not supported as Microsoft does not allow automatic app installation in the tenant during site creation.
Nintex Form migration is not available as part of Hyper Migration.