I actually don't think billionaires bother "offshoring" money, much, except as an emergency fund. Political leaders do. Billionaires just don't need to evade taxes, they can avoid them easily enough. I wouldn't take the risk were I wealthy, it is just not nearly worth it.
I'd have property somewhere half decent in central America for sure, legally, and might have some gold bars there in a safe, silver coins, etc.
I wouldn't illegally try and hide income, the slight chance of getting caught is just too high when I can avoid taxes easily.