obs OBS for online classes.

[Abigaroth]

I'm an university teacher. (in latin america)
I use OBS to stream and record my classes.
I have an FX-8320E and a Nitro R9 380 4GB, 400Mbps down and 10Mbps Up.

I use virtualcam to get the video output to zoom. 1080p 30fps canvas for webcam+ppt+realtime subs+zoom chat.
I think virtualcam uses the stream configuration (x264, main, veryfast, 4000 bitrate)
Also i record the classes with x264 2500 bitrate, and get 1.5GB per class, but i get some little artifacts if i'm also doing some stuff in the pc and i'm not very conformed with the quality for 1080 30fps. I want to try H264/AVC (AMD encoder) to get the gpu make some work.
The video then is uploaded to youtube and deleted the file (no edit), so i don't care so much about file size.
I'm not sure what kind of options for the AMD encoder should i use. I want around 5000 bitrate for the recording, but i'm not sure if use QP, CBR, VBR or VBRLAT.
Have anyone experience using AMD encoder to record video?
Thanks in advance.