What percentage of your portfolio should be crypto?

So as the title suggests, I'm wondering what % of my portfolio should be crypto? Should I include only the % market cap of crypto compared to stocks into my portfolio? (I say stocks because in my mind, crypto is just another asset class of equities, and is available to buy/sell on the open markets, such as stocks.) For example, if I invest in the world stock market index (VT), and Microsoft being 3.09T market cap takes up 3.86% of the world's stock market cap, BTC being roughly 1.23T market cap would take up 1.5% of the world's stock market cap. In other words, how do you determine what % of your portfolio crypto takes up? I'm a firm believer in index investing, and the efficient markets hypothesis. Well if there's such a large market cap in crypto, wouldn't it make sense to let the markets do the allocation for you? But do I just pretend BTC is another individual stock, and throw them all in the same mix?

Also, 2nd question, what's the best way to invest in crypto? Is there an ETF that just buys all relevant cryptocurrencies for me at market cap weight, so I can stay diversified in one fund? (preferably with a low expense ratio like stock market index funds). Or is it better to just buy the big players like BTC and ETH individually, and in which brokerages should I do this?