Thanks for the comment.
I understand that it is the third option I listed above. The firm I work for offers a Roth 401k by allowing after-tax contributions to a Traditional 401k, followed by an automatic in-plan Roth conversion into a Roth 401k account on the same day. I can contribute up to $36,500 in after-tax dollars to a Roth 401k (via the in-plan Roth conversion) if I have already maxed out my contributions to a Traditional 401k at $23,500, assuming a company match of $10,000. This will make the total contributions $70,000, which is the 2025 limit for 401k plans.