Stremio works with plugins. There's certain plugins that are able to fetch contents directly from torrent downloads, so the typical warnings about torrenting apply there (not to receive an undesired letter on the mailbox).
However, that same plugin is able to use some paid for services that download the torrents for you, which is safe(r).
IMO if subtitles aren't needed, it does pass the wife test once it's all configured. Subs wouldn't pass it though; it's common having to fiddle with sync settings to fix them. Chromecast casting definitely doesn't pass the test either: it is finicky, it resets the connection completely for each change (like seeking or changing subs), and it very frequently ends up erroring out with issues.
Ah, so realistically it's only likely to be a good UX when combined with a paid download service. I think I know which one you're referring to (at least, I only know of one such service, which I learned about from Reddit).
I have an Amazon Fire Stick, which works flawlessly with Plex across my local network, so hopefully Stremio works as well on it too.
It passes the wife test with certain add-ons. The good thing is once you configure it on PC with add-ons, settings persist over TV, mobile and Mac apps.
