I want to unlock the ability to view content on my mobile device. I can do that with a one-time purchase (payed with google opinion rewards) or with a subscription. I want to unlock the ability for my entire family though, across multiple devices. Do I have to pay the "one-time payment" for every device? If so, the plex subscription might be worth it. Is there any other major benefit to having a plex subscription?
Regarding downloading from other people's libraries, I believe they need to allow you to do so. I have a library that was shared with me, but I can’t download anything from them, although I can save it “offline” via the Plex app. The unfortunate thing is that the offline function doesn’t not work very well at all, it works about 20% of the time for me on iOS and Android.