TransitGateway supports Inter as well as Intra-region Peering.
See below blog for more information on this topic:
As for Peering you can do fully mesh of TGW peering as shown in the Whitepaper below:
Typically 1 TGW per region is used but yes, technically you can have multiple TGWs within 1 region and can do Intra-region peering between them.
AWS Transit Gateway Peering Daisy Chainasked 25 days ago
Can a VPC be attached to multiple TGWs?Accepted Answerasked 3 years ago
Transit Gateway Inter-region Peering PricingAccepted AnswerEXPERTasked 3 years ago
Transit gateway & VPC peering - IP forwardingAccepted Answerasked 3 years ago
Transit Gateway to Direct Connect Gateway to Transit GatewayAccepted Answerasked 2 years ago
Moving to AWS Transit Gateway from VPC PeeringAccepted Answerasked 2 years ago
AWS Transit Gateway peering encryptionAccepted Answerasked 3 years ago
AWS Transit Gateway attachment pricingAccepted Answerasked 2 years ago
Does AWS Transit Gateway peering supports Jumbo frames (MTU)?Accepted Answerasked 2 years ago
Transit Gateway Peering - Cross Accounts Not Sharing Payer IDAccepted Answerasked 3 years ago