The Rush Tiny Tank is a nano class VTX that has power output options of 0, 25, 100, 200 and 350mW output. It uses smart audio for parameter adjustment via betaflight OSD and has lock on technology that supposedly helps the signal. Perhaps more importantly it is very, very small and very light (1.6g). I used this VTX for my recent ultralight 3" TP3 build which I documented here.
Rush FPV as a brand is relatively new but made a huge splash with their premium full-sized tank VTX. Many found these vtxs as good if not better than the best-in-market TBS unify VTXs but as the name suggests, more robust. They followed the initial Rush Tank with the Rush race (similar but no mounting points and recently the rush mini 20mm mount. Their latest version is tiny tank reviewed here and at 1.6g is designed for micro builds or even racers (where 350mw is much more than you are allowed to run anyway). For me it is a perfect size for a toothpick build where keeping it light is the build. Due to it's small size install was simple and I was glad to see it offers multiple wiring options as below - mounted in line with camera or separately to the flight controller.