You have two questions with a third, implied question:
1) In what order should we contribute funds to various investment vehicles (pre-tax retirement, post-tax retirement, taxable investment)?
2) Where should we keep the investments (Vanguard, etc)?
a) What should our allocation be (stocks/index funds, bonds, REIT, etc)?
The first question is basically a question of math. Given your income and tax situation, how can you get the most bang for your buck? Make sure you start by maxing out any employer match - you will not beat a 100% return. Next up, you will likely want to maximize all other pre-tax retirement contributions, but this varies with tax situation. Many in the FIRE community likely have intentions of minimizing expenses, and living off less once they retire. So money that is in pre-tax retirement vehicles can be migrated into post-tax with very little tax impact. (You'll want to look into a Roth conversion pipeline if you retire before 60; otherwise 401k pre-tax can be withdrawn after 60, and as long as you keep the withdrawals low enough, your income tax will be minimal.)
The "conventional" wisdom for those that spend a lot AFTER they retire is that you might actually pay more tax then, so you might want to contribute more to Roth (post-tax) now and be done paying taxes already. But this is usually not a great fit for us.
Given that you 1) Max out employer match, 2) take advantage of pre-tax contributions, then you can 3) make use of Roth contributions and finally 4) put any leftover post-tax money in your own investment accounts. (The last two steps are important because you'll need some post-tax money available when you retire, particularly if it's before you've turned 60 and can't get to the pre-tax stuff yet.)
Now, with all this money in those various vehicles, you also want to know "where" to keep it. The easy answer is Vanguard, though you will have to do some research to decide on asset allocation that meets your goals, your risk tolerance, and how much time between now and retirement. From there, you can use Vanguard index funds with a split between Index funds, Bond funds and even REIT funds if that suits you. This takes a small learning curve to set up, but then you just check in every 3-12 months, see if the allocation is still where you want it for where you are on your journey, and if not, make some small changes (sell some stock index funds that are up to buy bond funds that are down and vice versa) and you're set.
Hopefully I kept that simple enough to give you a primer, and when the simple stuff sinks you, you can dive in and ask more specific questions about exactly where, exactly what funds, exactly what allocation, and how often you should rebalance.