1. Can you get around CRS by simply purchasing a Caribbean passport and using it to open personal bank accounts or EMIs anywhere without getting reported to your main country?
2. Are business account balances reported under CRS if you're a 25%+ shareholder?
Passport on its own won't help much. For most people (mainly non-US citizens), it's all about tax residence. Having a Vanuatu passport and living in Germany doesn't change the fact that German law applies to you.
Second passport as a way to avoid CRS doesn't really work, since the bank will also want to know where you live and many also ask about other citizenships. There are grey areas where for very wealthy clients, a bank might look the other way and not ask about second passport. But residence is always checked.