But how do you even access the plugins page now all I get with opera://plugins is this site can't be reached

Plugins page has been removed by Chromium since it became kinda obsolete.
There are sections for Flash and PDF viewer in Settings.
For Widevine you can use opera://components.

im trying to watch netflix and it says that Widevine is disabled, how would I enable it?

Netflix works fine on all my other browsers. Turbo mode is disabled. If I go to components, there is no way to enable or disable Widevine Content Decryption Module. How do I fix this error?