Only Legal Name and PAN number migrated from VAT during GST registration, both of which are non-editable fields.
The other details are open for you to enter as per the documents uploaded along. Thus in your case, in my opinion, you should do the needful as per VAT Laws ensuring amendment of the address and get an updated RC issued. After that, you may upload the same in GST Portal and mention the new address therein. In this case, there would be no hustle in GST migration and changes thereafter.