hey - if you want to stream with AMD VCE you should stick to the OBS VCE fork
https://obsproject.com/forum/threads/obs-studio-amd-vce-bitrate-problem.45454 shows the problem with Studio - but a Dev said its still in an experimental phase and not to use for STREAMING yet.
you can record with it - what looks great, but if you want to stream you still need OBS VCE fork (https://obsproject.com/forum/threads/obs-branch-with-amd-vce-support.13996/)
you can use my settings with most GCN 1.0 (or higher) Cards for 720p30 (i use HD7970) and just have around 5% CPU load
here 2 examples
ps if you have a newer card you can improve quality even more (i have to upgrade when Zen arrives)