Your due diligence should be the same as for a financial advisor handling your USD. Bitcoin is big enough now that they'll have a playbook for it. Don't hire a "crypto" professional.
If that's the case, I'm afraid I don't know what you should do. I can tell you, as a random internet commenter, that the companies I mentioned are reputable and operate in many countries around the world. There is a tail risk that they, or your traditional bank account, freeze your funds for "suspicious activity," and that's the case where having someone working for you is most useful. I'm not sure how you should bootstrap trust in your particular situation, I'm sorry. Good luck.