Funny thing I read today "cash out legally without paying tax".

You should read
tax avoidance and
tax evasion, what you said above you're trying to do tax evasion aka illegal way to not pay tax.
Let's imagine this, if you asked to fill an information or asked by authority, will you be honest with everything? like they ask where were you at when you got that 2.5 BTC? how do you got that coins? etc, if you trying to create fake stories, you're doing tax evasion.
People who do tax avoidance won't need to create fake stories because they only trying to lower their tax from the existing regulations.