1. IRA includes
(a) traditional 401K and (b) ROTH 401K.
2. 401K includes
(c) regular 401K and (d) ROTH 401K, total cannot exceed 20500.
(e) after-tax 401K, if your employer offers it, you have to max out 22500 above, then fill $20500-58000 in after tax 401K. Provided
After-tax 401K has no tax deferral function at all, you pay tax on principal and you pay tax on earnings. The benefit of after-tax 401K is that (1) it is shielded from lawsuit (2) doesn't count as college financial aid.
MEGA ROTH backdoor: You can rollover (e) after-tax 401K to (b) ROTH IRA or (d) ROTH 401K, in a number of situations. Including after termination to ROTH IRA, or in service rollover to ROTH 401K, if your plan allows it.