I can't say as I'm not familiar with Preact signals, but I do know the Angular team brought on the author of SolidJS to implement signals in Angular. Though I think I remember reading at some point that Preact signals were essentially directly ported from SolidJS, so they're likely similar if nothing else. (Someone correct me if I'm wrong)
Neither of those things are true to my knowledge... I can find absolutely no evidence of Ryan Carniato being involved with Angular Signals (nor did I hear anything whilst they were being developed) and Preact Signals certainly weren't a port of Solid. Same name but internals share nothing and if anything, Preact's signals most closely resemble Vue's refs in API (though completely different internals -- there was no porting).