Is it meant sit in vaults, like gold? Or is it meant to transact regularly, like a currency?

It's meant to launder money.

I say that in all seriousness. Piketty burned an entire chapter in Capital in the 21st Century determining the size of the black market and estimated it at 50% of the white market. If 10% of black market transactions are executed in bitcoin, Bitcoin's market cap would be 70 trillion dollars. There are 18b bitcoin in circulation with a market cap of $430b. There can never be more than 21b BTC. We're looking squarely at Drake's Equation here: we have a stack of bullshit factors that give us a scientific number but "ponzi scheme" or not there's a fair amount of runway even if you presume BTC will never be anything but thermonuclearly illegal.

I don’t think you can have both at the same time and it be a stable investment vehicle with better returns than real asset classes.

"Stable investment vehicle" is a relative term. No matter how you define it, though, it certainly doesn't apply to Bitcoin at the moment. "Real asset classes" is also a relative term. There was a time when ETFs weren't "real asset classes." The 401(k) is an accidentally-discovered tax loophole. Pets.com is a cautionary tale; Chewy.com has a $43b market cap doing the exact same fucking thing 20 years later. You're effectively saying "it must be bad since I don't understand it, and since it must be bad I don't have to understand it."

mk can talk at length about crypto. So can I. Been there, done that. But you're never going to get more than a beatdown when your basic approach to the discussion is "this is stupid and illegal, and everyone involved in it is a stupid criminal." I've been called a stupid criminal by accountants, financial planners and immediate family members for owning crypto so if I want someone to berate me for making money I can get that job done by far more important opinions than yours.