What do you do when you leave a company with your 401k? Do you roll it to a personal account or what?
You can convert old 401k into an IRA account
Conversion into a self managed IRA account often gives you the flexibility to buy/sell almost any stock/ETF on a tax deferred basis.
ROLL TO VANGUARD. DONE.
Don't roll if you intend to backdoor roth ira
What does this mean?
Look into the backdoor Roth ira pro rata rule
Depends on the custodian, choices available, fees and expense ratios, and if you want to do a conversion ladder down the line from an IRA. There's also an option to roll into a solo 401k if you want to get creative. In general if your new employer has good fund selection, they will have lower expense ratios than an IRA.