My advice is to not overthink it and do what works for you.

IMO,

don’t use a pkg directory. It only makes your import paths more unwieldy.

Don’t use internal unless you have a package that is an awkward implementation detail that must be shared between packages for expedience. Usually this can be factored away with some effort but sometimes it’s not worth it.

Do use cmd directories. They make it clear what “go install” will do.

But otherwise really just pick any approach and move on with your life.