The catastrophic error IMO is:
Five years from when you open your account there are options for taking gains out tax-free even if you’re not 59.5 yet. You can take “substantially equal periodic payments”, but there are also ones for various kinds of hardship.
For Roth you mostly can’t take out gains tax-free. The hardship ones are limited, and SEPP doesn’t let you access much of it early. The big ones of Roth conversions and just eating the 10% penalty only work for pretax.
[As an aside Roth accounts are worse for most people vs pretax for multiple reasons, e.g. pretax comes with an option of converting or withdrawing in low income years at low tax rates. More details here.]
In #1 if you start with $100k then it’s $200k at the time you convert, and you pay $48k (24%) in taxes leaving you with $152k in your Roth 401k. It grows to $198k, you withdraw $152k and you have $46k of gains in your Roth 401k.
You pay taxes on the amount you convert, either from outside funds or withdrawals to you. If you convert $X you owe taxes on that as ordinary income, so you can convert $200k and pay $48k in taxes from outside funds. This makes pretax better.
Re your assumptions, they are not great for an AI-pilled saver. Someone who believes in short AI timelines should probably be investing in AI if they don’t have decisive deontological objections. NVDA is up 20x in the last 5 years, OpenAI even more. On the way to a singularity AI investments will probably more than 10x again unless it’s a surprise in the next few years as Daniel K argues in comments. So their 401k should be ~all earnings, and they may have a hard time staying in the low tax brackets you use (moreso at withdrawal time than contribution time) if they save a lot. The top federal tax rates are 37% for ordinary income and 23.8% for capital gains.
Paying the top federal income tax rate plus penalties means a 47% tax rate on early withdrawals from the Roth vs 23.8% from taxable. I.e. every dollar kept outside the the Roth is worth 44% more if you won’t be using the account after 59.5. That’s a wild difference from the standard Roth withdrawal case where there’s a 0% tax rate.
A substantially larger percentage in Roth than the probability you are around to use it and care about it after 59.5 looks bad to me. From the perspective of someone expecting AI soon this advice could significantly hurt them in a way that the post obscured.
AIs showing bits of unintended motives in experiments or deployment would be a valuable piece of evidence re scheming risk, but such behavior would be trained against, pushing scheming behavior out towards the tails of takeover/escape with the power to resist modification. The tendency of human institutions to retrain or replace AIs to human preferences pushes towards misaligned AIs having ~0 or very high power.