What would be the most efficient way to retopo this mesh? Should I just make the low poly version by removing the modifiers then bake, or start from scratch like how most people retopo a human?
edit: I'm going to use it as a video game asset.
The geometry looks OK. You do not need to retopologize this. It can be improved by editing and removing some loops or sliding some edges(Shift + V) and merging some vertices, but I don't think you need to do a lot here. Starting from scratch seems unnecessary for many purposes. Obviously, since you did not tell anything about your context or what you are planing to use it for, it's hard to say for sure.