I made a queuing theory calculator for this: https://joshmoody.org/blog/number-of-agents/#number-of-agent...

Although you'll have to mentally replace the word "agent" with "PR" for it to make sense in this context. The math is the same. It all boils down to how much those context switches costs you. If it's a large cost, then you can get a huge productivity boost by increasing review speed.

In the "show calculations" section, the amount of wasted time caused by context switching is the delta between the numbers in the phrase "T_r adjusted from 30.0 to 35 minutes". That number is increases as context switching cost and "average agent time" (AKA "average PR review time") goes up.