In my opinion Draw Things is the best stable diffusion app currently available for macOS/iOS. It's free, it is available in the App Store, it manages downloading models and weights, it supports a wide selection of popular models as well as custom weights, and it supports inpainting, text2image, and image2image.
It has some oddities: it uses a sqlite database to store generated images rather than the more traditional files, and the UI is idiosyncratic. You have to follow the author's twitter feed to learn how to use the advanced features.
It has some oddities: it uses a sqlite database to store generated images rather than the more traditional files, and the UI is idiosyncratic. You have to follow the author's twitter feed to learn how to use the advanced features.