That's fine if you are willing to sell in big chunks and keep track of the basis in the chunk you sold, which isn't simple. But I know people who advocate using crypto as their cash account and keeping everything in crypto, selling it constantly as they pay expenses. That's an accounting nightmare of the tax preparer and at your expense.
I'm not sure what you are saying. Are you saying if you buy one unit of Bitcoin, hold it long-term and then sell it you have a simple long-term capital gain? That would be true but if you buy a hamburger and fries or pay your rent with your crypto account you have quite a different story.