Simply put it seems like the last couple of driver releases have broken VCE encoding (for me anyway) in both OBS and relive. The option to use that particular encoder seems to have vanished. This is the case with both my r9 390 and Fury cards. Anyone have any similar experiences?
Nothing has changed, the Video Coding Engine (VCE) is still used to encode and the output is in H.264 (AVC = Advanced Video Coding) format. VCE is the component you used on the graphics chip to record your gameplay via Relive Crimson software.
For issues relating to OBS you'll need to contact the developer of that software.