I use Sonnet 5.5 and Opus 5.5 both on Medium to produce apps in Rust/Tauri all day every day on a $20 Pro sub, and absolutely these two models do a great job with that stack. I rarely run out of weekly credits, unless I use Opus 5.5 on high or ultra code. Medium does the job 99% of the time. Fable is good, but it'll never be as good as Opus when well prompted and with some iteration. I see Fable as a preview of what the next model will be able to do, but it's really not a good production model unless you have a lot of cash to burn.