You are doing great first and foremost!!! Don't forget that or think we all don't recognize that.
A few things before the advice part....you are still very young and may not be fully aware of the challenges of being older yet (health (far bigger concern than most 30 year olds truly understand), more limited career and job options, not having the same energy levels and so on....
That said, I didn't see HSA in your list of qualified accounts? Is that an option for you OR do you get government benefit or a PPO for health care? If you DO qualify for an HSA I would max that THROUGH PAYROLL DEDUCTIONS and put that 2nd in your pecking order just after getting the 6% 401k match. Why....HSA money is a tax deductive the year it goes in AND tax free coming out when used on health care (believe me...there can be A LOT more healthcare costs after 40 and that only goes up and up each 5 years as you continue to age). ALSO....HSA accounts when the contributions IS FROM PAYROLL DEDUCTIONS ONLY.....do not have social security or medicare withholdings (not even 401k's or IRAs get those....or roths). LASTLY.....HSA is ALSO a backdoor IRA....lets save you "oversave" in your HSA. At age 65...you can make withdrawals and pay income tax then ... making it an IRA essentially (you still got the federal/state tax break when you made the contribution AND the social security/medicare break).
Now for your brokerage funds.....do you have an emergency fund? I don't think I read about that. If not....get a HYSA with at LEAST 1 month of expenses ASAP....stop ALL brokerage contributions til you hit that. Ideally you have 3 months expenses .... but I think you could use your brokerage funds in the event of an emergency....but you REALLY need 1 month CASH or cash equivalent so you are not tempted to sell for super short term emergencies or forced to take on higher interest loans.
What to do after all that....personally THIS would be my pecking order if I were you (with the very limited knowledge I have about you lol)
1st* - top off emergency funs - 1 month CASH....then ideally additional months cash OR 4 months in investments (this covers your a** if there is a recession (investments drop a lot in value) and you get laid off
1st - 6% into the company 401k to get the full match
2nd - max HSA (if applicable)
3rd - max Roth IRA
4th - max 401k
5th - 529's and brokerage accounts
Notes:
I TOTALLY get where you are coming from with wanting the flexibility. HOWEVER....lets say you leave your job in 10-15 years.....you roll your 401k into an IRA and then you can do SEPP (substantially equal periodic payment) withdrawals until you hit 59.5.
https://www.investopedia.com/terms/s/sepp.aspThe only reason to maybe save into a brokerage for "flexibility" is for a mid term event (something 7+ years out) .... maybe you want to take a year or two off of working, buy a house or yada yada....and the event is far out enough to bounce back from down markets. That OR you want a "emergency fund" with aggressive growth....in which I would recommend AGAIN....1 month cash....4 months investment with the mindset that it will cover you for 3 months. Of course....as it grows....youll have more and more over time to cover you.