If you are trying to hide from the NSA or other nation states, you have a LOT of work cut out for you. There are basically two sub threat models: are you trying to hide from the dragnet (in which case, just using any obscure and relatively obfuscated communications mechanism will work) or the scenario in which you’re being actively targeted (in which case you need rock solid security from end to end). Keep in mind that the Security version of https://en.m.wikipedia.org/wiki/Analog_hole means the security of your networked device is just as important as your messaging protocol, and… good luck with that on mobile.
If you are just a small fish trying to avoid something with a court-admissible record (and don’t care about parallel construction) you’re probably fine with Signal, provided you understand that your counterparty can just give you up.
I hate to bring out the “nothing to hide” argument because I disagree with its premise from a moral standpoint, but from a practical standpoint, I recommend avoiding having “directly targeted by the NSA and needing to avoid it” as your threat model to begin with.