Before I started work on it, I looked around at all of the available options, and none of them really fit what I wanted:

- easy to use

- fast

- not a huge desktop app

so I decided to make my own! AirmailAI (if you're not running it locally) is a one-click install from the Chrome Web Store, the TTFT overhead is within 50ms of raw https API requests, and the install size/memory requirements are very reasonable (<2MB on disk, ~60MB RAM while running).