Thank you for your reply and sharing those resources.
Perhaps it would be helpful to me if you could expand on your statement at the end of your post. What do you mean when you say, "It [penal substitution] pits Christ/God against Father/God as if there are two conflicting wills in the Godhead..."? From the second link you posted, the author writes:
1. Penal substitution compromises the deity of Christ and puts a rift in the Trinity
If Christ died for, and is our solution to, our sins against god the Father, then what about our sins against Christ? He’s just as god as the Father is. or our sins against the Holy Spirit? With penal substitution, God is pitted against God, either dividing God (and thus destroying the Trinity) or saying that Christ isn’t fully god.
Is this the basis for your referring to "conflicting wills in the Godhead" as a consequence of penal substitution? If so, I suppose I fail to understand the theological grounding for an interpretation that allows for a particular sin to be regarded as an offense against one person within the Trinity and not the others, who are coequally God and have the same Divine nature and perfect righteousness. If sin is any failure to conform to, or any actual violation of, the law of God, then all sin is an offense to the Triune God as Father, Son,
and Spirit; not Father, Son,
or Spirit. I do not see how, on the view of penal substitution, the Trinity is rent apart.