Terminology: in the tax preparation industry, "pre-tax" and "post-tax" usually only refer to contributions (not account types) that are or are not (respectively) excluded from current income. Earnings in the account over time are either tax-free or tax-deferred (depends on account type and what the distributions of said earnings are eventually used for), and distributions are either taxable (possibly with penalty), or tax-free.
HSA - these are indeed like a Traditional IRA "on steroids", but calling it "a pre-tax account that is only allowed to spend money on healthcare related items" is incorrect. Distributions from HSAs can be spent on anything, but they are taxed as ordinary income if not spent on medical expenses. Also, before age 65, distributions not spent on medical expenses receive a 20% penalty as well as regular tax. So, at age 65, it essentially turns into a regular Trad. IRA (distributions are taxable), except if you want, you can pay your Medicare premiums and other health expenses tax-free from the HSA.
An HSA can either be through an employer or opened directly by the individual. If there are other tax-advantaged employer health expense arrangements (or Medicare coverage), contributions to HSAs maybe limited. I have known of the benefits of HSAs for years but always felt the employer subsidy for non-HDHP insurance coverage was a better deal; however if you don't have employer insurance coverage, HSAs are probably the best way to go. See IRS Publication 969 for more details.
401k - "No access until minimum age 55". But what's worse, there is essentially no access at all while you are still employed with that employer, in other words you can't take any money out unless the plan allows it (and most don't), even if you are willing to pay tax & penalty. (There may be a loan option, but that is a bad idea for several reasons).
"For self-employed people, I would look into a SIMPLE 401K. " For self-employed people with no employees of their own, a solo 401k (401k with only the owner as a member) allow for much higher contribution levels than SEP-IRA, especially at lower profit levels.
IRA - "with an income of $140k, one cannot make ANY contribution, at least directly. " False. With even a little earned income, any taxpayer can make a contribution to a Trad. IRA no matter their total income (AGI). What the income limit pertains to is the deductibility of contributions to Trad. IRA (pre-tax or post-tax). And there is also an income limit that prevents any contributions to a Roth IRA at all. Until recently there was an age 70.5 cut-off on making contributions.
" IRAs do not allow access until minimum age 59.5" -- well they do, but with a 10% penalty (other than a few exceptions for special purposes). One feature not many understand is that at any age, you can convert money from Trad. IRA to Roth, pay the tax, and then after five years you can take that money out penalty-free from the Roth. So if you can afford to pay the tax now and wait five years, you can get some or all of your money out of your IRA at any age without penalty.
Section 529 plans aka QTP - "One can switch beneficiaries tax free up to $70k (double for couples) by "front-loading" or "superfunding", although there are federal gift tax consequences". This is really mixing up several different things. First, it is extremely unlikely that anyone would end up paying any gift tax on contributions to a 529 plan, although there may a tax reporting requirement (Form 706). Also, switching beneficiaries does not have anything to do with a $70K limit. What is being referred to is that one can contribute up to five year's worth of gifts all at once, each under the annual reporting threshhold for gifts, instead of having to spread the contributions out over five years to avoid reporting (and again, even with reporting, it is extremely unlikely any gift tax would be owed).