There’s a few methods here - and it’s going to depend on your mix of retirement accounts (ROTH vs Trad vs HSA vs non-tax advantaged). There’s lots of tools to help plan scenarios - I particularly like ProjectionLab. I would also recommend hiring a professional that can assist in the planning and especially taxes during early retirement.
For SEPP 72T you need to make similar withdrawals every year for at least 5 years or until you hit 59.5 of age. My plan is a mix of SEPP 72T + non-tax advantaged accounts for 5 years. During those 5 years I will also be making ROTH conversions from my Trad accounts. Once the 5 years are up - I will continue my ROTH conversions but can finally start withdrawing the money I converted 5 years ago (this is a ROTH conversion ladder).
I was a bit of a late bloomer and spent my 20s working my way into tech - so I won’t retire at 45 - but am on target for 50ish.
If your employer offers a match, you should absolutely contribute up to the maximum match (it's free money after all), but not a penny more IMO. There are much, much better vehicles for parking your money than retirement funds.
I started doing this when I got a raise and realized pretty much half of my raise was going straight to taxes, whereas I could invest it all if I just upped my 401k contributions.
Historically, tax rates have gone down over time, not up. Especially in recent history.
You do pay a reduced tax in retirement because you're able to blend your income. You defer taxes on the 401k until requirement, but you pre-pay taxes on a mega backdoor/roth, so if you need 100k of income in retirement you pull 50k from 401k and 50k on the roth and only pay taxes on half of it, putting you in a lower bracket.
Having the pretax money to grow before paying taxes on it is greater than having post tax money and having less to compound.
The alternative to tax advantaged places to park your money for retirement is strictly worse than non-tax advantaged. In a 401k you pay taxes only in retirement, for roth's you pay taxes only with your paycheck. In a brokerage, you pay taxes at your paycheck and then you pay taxes on withdraw for your cost basis.