I am currently in the process of switching my task management software from Things to taskwarrior. (Cultured Code introduced cloud synchronization, even without encryption, in Things 2, so I'm out).
I do not adhere strictly to the GTD method but one concept I find very useful is the Inbox. Tasks which are quickly captured land in the inbox first. From time to time, you review your inbox from time to time and sort the tasks into the appropriate projects.
What is the best way to implement this in taskwarrior?