We have tried to do windows file transfer between 2 spokes but the performance was very poor and was only able to get 3-4 Mbps. Spoke 1 & 2 both connects to the same hub.
Spoke 1 has 45Mpbs upload
Spoke 2 has 300Mbps download
Hub uses 100Mbps DIA.
Use Microsoft File Sharing to send a file from spoke 1 to spoke 2 and the transfer rate was only 3-4 Mbps.
The issue will go away if we do auto vpn full mesh, so it's not the ISP issue.