I want to build an indexer, search head, and deployment server on our own (not Splunk's ) AWS VPC. The overall question is, how do I configure an On-Prem Intermediate Forwarder (HWF) to connect to the Cloud version of the indexer? Just looking for a general answer, I don't know what our Cloud service offering provides (VPN, SSL etc etc).
You would need to configure the AWS instance with an elastic IP (global IP) and allow the required TCP ports through. From there, configure your forwarder to point that indexer from your on-premise HWF.