Thank you for your reply. Really appreciate it! I understand the mechanism of the "backdoor roth". I, however, was speaking about the so called "mega-backdoor roth" which utilizes the allowance to contribute after-tax to a 401k plan (if the plan allows it). These contributions are then converted and rolled over to a roth IRA which essentially allows for adding to a roth IRA beyond the annual direct contribution limit.
In my case, I would like to first convert these after-tax 401k contributions to roth (still in the 401k plan), and then at a later time (presumably with some gains) roll these over to my roth IRA. In your response you mention that there's no tax when rolling over from roth 401k to roth IRA, and can be done so as long as my plan allows for my roth 401k funds to be transferred (which they do), then there wouldn't be any tax implications (beyond the initial conversion from after-tax). So it appears what I'm planning on doing will work. Thank you again for your response.
