I understand them both to be based on Chromium at this point. Chrome already has support, so if the Brave/Opera browsers want it it's pretty much just a flip of the switch (Opera may already have it, I think).

Basically if your browser lists any kind of Content Decryption Module (usually something called Widevine) among its plugins, you have EME support.

Brave and Opera both use the Blink rendering engine from Chromium/Google. Therefore, you may see this new DRM W3C standard in Brave and Opera.