I think the OP is still confused about the concepts.
Vanguard, etc. are places to hold your accounts.
TIRA, 401k (pre-tax, pay tax on withdrawal), Roth IRA, Roth 401k (post-tax, tax free withdrawal), taxable (post-tax, capital gains tax) -- buckets held at the places like Vanguard.
Stocks, bonds, index funds, managed funds -- investments that are held in the buckets.
How low is your income? Are you eligible for EITC? What are your taxes like?
If you owe tax and want to reduce your AGI, either 401k or tIRA will reduce your taxable income. Roth and taxable will not. If you only have a small amount to invest, choose the more efficient one. No match and high fees means tIRA at Vanguard could be more efficient for you.
If you are eligible for the EITC, 401k may be better than tIRA, makes you eligible for a larger credit. A large taxable account can make you ineligible altogether.
If your AGI is low enough that your taxable income = 0 (after deductions and exemptions), Roth accounts would be better - no need for the tax break, tax free forever.
Only once you have run out of tax advantaged space would you move on to taxable accounts. So only after maxing 401k AND IRAs for both of you.