You can’t own 50% of more of a company you invest in using your self directed Roth IRA. So, QSBS is great for founders who own 50% or more.

Just be your own custodian. Dont conflate the limitations of third party custodians with the actual law, which is way more flexible. You can move Roth Ira funds around willy nilly. You can have a literal stack of cash on your desk labeled Roth Ira and invest in almost anything. Its just the consumptive purchases that would be a problem.

To your question, it is always better to have free and clear money with no restrictions, which means 0% tax now is better than locked up funds that you also wont have to pay taxes on in the future. Retirement products and trusts are judgement proof though sometimes even against ex spouses, not IRAs though), so if you have or expect to have creditors, better not to have assets in your name. Even better is to only have debt in your name so you can just tell people to get in line, or discourage them from ever bothering with the courts at all. Stuffing Roth IRAs are good for that.

Are there filing or record keeping requirements to being your own custodian? I imagine the process is somewhat more involved than labeling the stack of cash “Roth IRA”, or is it really that simple?

Just be able to pass an audit

So people generally like a paper trail for that

Is there a write up of how do be your own custodian? I'm paying a trust company annual fees to basically file irs form 5498 for multiple iras that only own an llc. I would pay money for information on how to do this.

I tried to look into this and as far as I can tell you cannot actually be your own custodian for IRAs. There are of course self-directed IRAs where you can hold non-traditional investments, but they still require a third-party custodian.

you go tax free after 5 years of ownership for up to 10 or 50 million or something. so you can ball out as a young person (without paying taxes)

The "over 55" restrictions on Roth withdrawals isn't a problem for me.