If you're streaming, use CBR as every platform recommends it and it's a reliable form of Rate Control. If you're recording and need to be high quality, use CQP if the file size is no issue, or VBR if you want to keep file size more reasonable.

Should I use CBR or VBR OBS?

Use VBR or CQP for recording. With CBR, the bit rate is going to be constant regardless of content. VBR allows for fewer/more bits to be used when necessary and CQP allows for constant quality (something like that). CBR is good for streaming but that's about it.

What FPS type should I use for OBS?

I recommend 720p60 (720p, 60 fps) or 1080p30 (1080p, 30 fps) in OBS. For 60 fps use the x264 preset 'veryfast', profile 'high' and Tune 'none'. For 30 fps you can try using the x264 preset 'fast'.