Confused about forking ethereum for an initial private network.

So I am a software engineer and I want to fork the ethereum source code for a custom coin. However all of the tutorials on Hyperledger Besu, geth, etc are unclear, or trying to sell something, or offer something as a service, which I don't want or atleast want to avoid. The last time I worked on blockchain was before ethereum really took off, but it seems to be the best to modify for my use case.

1.Whats the best tool to use for a custom coin based on ethereum, with an eye of eventually allowing public nodes? What avoids all of these ethereum middleware as a service providers.