Could anyone help me understand Vnet-to-Vnet dynamic communication?

Question

I am setting up a hub and spoke topology and I want transitive communication between spokes, which are peered to my hub. I am having a tough time figuring out what a few settings do and the requirements here. I understand that I need to have UDR's on each spoke that point to the hub's NVA/gateway. Some settings confuse me in here though.

Primarily:
"Use this/remote virtual network's gateway or Route Server" setting in peering config - what will this do and is it related to BGP?
"Propagate gateway routes" section in routing table config - Does this propagate routes INTO the spoke's routing table, or will it propagate the spoke's routes OUT to other routing tables?
"Enable BGP" in the VGW or NVA config - Do I even need BGP if I'm not connecting to on prem?

Could anyone clarify how these settings interoperate with each other and what is necessary vs what is optional?

Answer 1

By default VNET peerings are not transitive, as you already know. Setting up a VPN Gateway to do the routing between spokes in your hub-and-spoke setup is expensive and capacity-limited and cumbersome to set up.. I think there are better solutions to achieve the transitive communication:
Create a mesh network, by peering all spokes directly
use Virtual Network Manager (https://learn.microsoft.com/en-us/azure/virtual-network-manager/overview)
Use Azure Firewall to route all allowed traffic

If you want to know more about network manager, see this excellent video: https://www.youtube.com/watch?v=qNn83S55WHQ