Is NouveauPG available from the App Store?

You can purchase NouveauPG from the Mac App Store. I would prefer that you try it out first by downloading the trial version before using the reviews to express buyer’s remorse. https://itunes.apple.com/us/app/nouveaupg/id968220622?mt=12

How do I know you’re not using NouveauPG to trojan horse my computer?

Unlike GnuPG Tools, NouveauPG uses the App Sandbox in OS X to isolate itself from your data. NouveauPG cannot access the network or any files that are not selected by the user with the system file selection boxes. The only way for data to get in or out is by manually selecting a file, or using the clipboard.

Will you open source it so we can be sure?

Sure, the full source code is available on my GitHub

I personally don’t trust AES, can you provide the option to use Twofish/Serpent/etc.?

No. This is the sort of thinking that leads to confusing encryption software. The security of AES is not at all controversial from the informed perspective.┬áIf this concerns you, you should compile and run gnupg v1 (it’s easier to compile than gnupg v2).

There are way bigger issues with GPG Tools than any encryption algorithms it supports.