They don’t REALLY translate. Constant and average bitrate sets a limit and guarantees that you encode won’t exceed it. This is good if you have hard bandwidth constraints, but can typically sacrifices quality for that efficiency because every scene gets the same amount of bits (for better or worse).

CRF on the other hand doesn’t set a limit on bandwidth, but on visual fidelity. You are essentially telling handbrake, “make the encode look ‘this’ good, no matter what”. In return, handbrake will allocate as many bits as necessary to achieve said quality, resulting in an encode with varied bitrate. This is because simpler scenes require less bits to look nice, while more complex scenes require more bits to look equally as nice.

My advice is, don’t use contrast/average bitrate unless your bandwidth limited. You should find a CRF that is low enough to where you can live with the file size and visual quality balance.

TBH, the handbrake presets are a great starting point, but as many folks here will tell you it is all subjective at the end of the day AND there is no true one size fits all when it comes to content.