I'd rather go to Svelte for lower bundle size than Preact, better performance than Preact, and clearer code with fewer lines written than Preact.
Sure, I'd lose access to the React ecosystem, but I'd also gain access to the vast ecosystem of vanilla JS libraries without having to write/use a wrapper, so that's a wash. (bind:this is awesome!)
Yep, sure! Personally I don't like the Svelte programming model, and I like Preact signals a lot, and hooks are fine to me. But Svelte is definitely a good way overall.