Hello, I'm in a situation where I need to use the maximum security possible. What should I do?
What you want is this:
1) have a very strong pass phrase. it should be 20 characters long at a minimum.
2) choose "always require pass phrase to open encrypted messages"
3) when messaging people who don't use FlowCrypt, add a sufficiently strong password that you can communicate to them in some other way (a phone call, or WhatsApp)
4) use a full disk encryption on your device with a strong password
5) eventually move off US based email services
6) Linux, or at least a Mac, may be a better choice compared to windows
7) very strong passcode on your phone (I use an alphanumeric password)
8) use two factor authentication on all of your online accounts (to receive a text with a code every time you wan to log in, or use Google Authenticator or Authy)