Keeping an emergency fund in VPAIX or VUSXX?

We're building our emergency fund out, and it'll be around 40k. I'm wondering where to put it. Most of our money is in Vanguard, so it seems simplest to me to just keep it in Vanguard rather than a HYSA. I was thinking of VMFXX but after reading about state tax stuff, I figured I'd try VUSXX. I live in PA with a state income tax. I was also looking at VPAIX thinking it might have even fewer tax liabilities. Is that a decent option? Talk to me like I'm stupid! The impression I have based on some research is VPAIX will be more volatile than VUSXX so I shouldnt do it. Does that seem right?