Welcome to the Microsoft Q&A Platform. Thank you for reaching out & I hope you are doing well.
If you'd like to know how you can connect multiple sites to a VPN Gateway , you can follow this : https://learn.microsoft.com/en-us/azure/vpn-gateway/vpn-gateway-howto-multi-site-to-site-resource-manager-portal
The VPN Gateway will take care of the bandwidth and throughput, no need to add a Load Balancer here.
Cheers,
Kapil
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