Integration MM-ISU Good issue movement types

Hello!!

I have a question regarding the integration between MM and ISU

My customer is using MM-IM to manage the inventory in SAP, so when a purchase order arrives they create a GR with serial numbers which automatically triggers the integration with ISU and creates the devices in status ESTO.

I have not been able to understand yet how is this business process in SAP standard for the GI

The device needs to have the Status AVBL at the time of installation and usually this is done by a GI (201 or 261 movements as example) So the process should be like this as far as I understand

1. PO  - GR - GI -  Installation

I have read about movement types U61 and U62 but I am not sure how are they related to this process.

What would be the difference between using U61 or 201 movements for the GI?

Is there any standard transaction to do the GI & Installation in one step?

Hope you can help.

Thanks