As a security professional, I always tell people to assume everything they do while online is public. Would you mind if what you are writing was posted for the whole world to see? If you do, don't write it. I don't care if you send it through a protonmail.com account or not. If you are on the Internet, what you write should be considered seen by anyone.
The same is true with where you go on the Internet, what you're looking at, and what you're downloading. It's all public and easily tracked by governments and their agencies. Even if you have end to end encryption too, you can still have a key logger. Even the best phones will still track your location as well.
If you really want security, make the message on a completely offline system. Encrypt it there, transfer it by hand, and then send it. The other person does the opposite. As you said though, they can just forward that received message to a government agent. Worse, they could be the government agent.
Trust? I don't have much of it. Even when you whisper something in a loved one's ear, it is no longer a secret. Chances are, they will repeat it. Therefore, only speak of things you want to be repeated. Otherwise, keep your trap shut, or understand the consequences. haha
I'll resteem this to help get you some followers. There's a security channel on steemit.chat too if you ever have the spare time to network and engage through it. Please consider using the #security tag. Basically, look through the existing popular tags, and use them as much as possible but only when it is appropriate.
RE: When VPNs and encrypted messengers can't protect you...