What is in your Capital One account? If you have ETFs then you can transfer to Vanguard "in kind" to postpone the capital gains. Vanguard does charge a $7 commission to sell non-Vanguard funds, but it may be worth it to get out of high expense ratios. Or you can just leave them in your Vanguard account.
If you have a bunch of individual stocks you should probably sell before transferring. If capital one charges commissions you could transfer the account to Robin Hood, sell the shares for free, then transfer the cash to Vanguard and buy VTSAX. Robin Hood doesn't accept partial shares and some foreign stocks though, so you will have to sell those prior to transferring.