Edit: On further review it doesn’t clearly state if you buy a subscription if the apps get unlocked or if you still have to purchase the unlock.
Plex Features
Available Anywhere
Stream your media to your devices, anywhere, with a seamless and beautiful experience. Android and iOS apps require an unlock fee for full playback.
Edit 2: After digging into the support articles it makes it perfectly clear that if you purchase a Plex Pass and the subscription is active you will not be required to also purchase the app unlock feature and will get the unlock included for as long as the subscription is active. You can read more about what’s restricted and whats unrestricted here also.
Final edited reply…
Just had a bit of a look into this they do charge you to playback video files on certain platforms by making you purchase and unlock if you don’t have a subscription.
I had thought they got rid of this quite awhile back initially you had to pay for the Plex app on each mobile platform but it looks like instead of getting rid of the fee they just moved it to an in app purchase.
You should be setting up a Plex account regardless what option you pick.
Pay for a subscription or pay the app unlock. A free Plex account will be required also if you pay for the app unlock to allow you to access your media outside your network.