Still looking for help guys.
Bases on kenaces answer,
I confirmed that both Betterment, and my 401k are tracking the same indexes (CRSP small / mid cap indexes). This isn't ideal.
New questions:
kenaces mentions schwab doesn't report to the IRS in retirement accounts. Betterment isn't a retirement acct, just a normal taxable account. And for now, Betterment would be the only account making any sales. Do you I need to check that fidelity (401k) won't report any purchases within the retirement (401k) account?
Would I be better off switching out the 401k funds back into a target year fund to make sure it can't interfere with betterment? I'd really rather keep the higher return, lower fee vanguard funds if possible.