In Opera 12.x there was a built in ad blocker with an option to manage the block list. There was no automatic block list update like in current version.
12.16 was the last version built around Opera's native engine. Next major release (version 15 if I am not mistaken) was built using the Chromium engine and the adblock feature was dropped.
I am glad that adblock is back, but an option to add a site to the list locally is a must.
Integrated mail is so yesterday... a path being taken by Vivaldi and undoubtedly wanted by an exceedingly small group of users (translation: it will never catch on beyond a group less than 1% of the user population). Opera needs to spend its time on innovation rather than returning to a suite of the 90's.
I enabled Plex settings to: "Prefer the HTML5 video player over the Flash player"
And also disabled flash to make sure it wasn't falling back on flash to test it....