The ability to make deductible contributions to a traditional IRA is unaffected by your taxable holdings or lack thereof. See https://www.irs.gov/Retirement-Plans/IRA-Deduction-Limits.
Vanguard (or Fidelity, or Schwab, or...) will be happy to provide any combination of taxable, tIRA, Roth, etc. accounts for you - just make sure the IRS regulations are observed. ;)
In other words, must each different Vanguard investment be 10k minimum?
Vanguard IRA only has a 1k minimum to open (although some of the funds have a 3k minimum to invest in so your investment choices with only 1k is limited)
The following minimums apply to individual and joint accounts, Roth and traditional IRAs, UGMA/UTMA accounts, and most other account types.Investor Shares $1,000 for Vanguard Target Retirement Funds and Vanguard STARŪ Fund. $3,000 for most other Vanguard funds.**Admiral Shares $10,000 for most index funds and tax-managed funds. $50,000 for most actively managed funds. $100,000 for certain sector-specific index funds.