Overlap-CIDR between two VPC

Yes Aviatrix does support overlapping. All the use-cases you listed are cases we see from other customers as well. There are different design possibles based on your requirement. Start from this doc and see if it fits your need. If not, we can have a zoom session with our SE as well

https://docs.aviatrix.com/HowTos/site2cloud_faq.html?highlight=overlapping%20IP#are-there-any-tech-notes-on-solving-overlapping-ip-addresses