VPC to Customer premises:
AWS Direct Connect or
VPN connections from on-premises
connecting VPCs in different AWS Regions using either
AWS-managed networks or
non-AWS networks ( Private network/Internet-ISP = AWS Direct Connect or VPN connection )
Single Region Multi-VPC Connectivity
https://aws.amazon.com/answers/networking/aws-single-region-multi-vpc-connectivity/
Multiple Region Multi-VPC Connectivity
https://aws.amazon.com/answers/networking/aws-multiple-region-multi-vpc-connectivity/