How light should light stocking be

[Navyblue]

I am in the midst of stocking up a 120G. And intend to stock light. My question is what is the maximum number of fish that I can have and still consider my tank "lightly stocked".

My personal rule of thumb for "moderate stocking" is about 1 small fish (that get no larger than 6" in the wild) per 10G. And any fish larger than that I'd consider that as 2 small fish.

Meaning in my 120G I'd consider 12 fishes that get no larger than 6", or 10 fishes under 6" + 1 fish that gets larger than 6", as moderately stocked. And lets say if I kept 10 small fishes I'd consider myself on the lighter side.

Btw I already have 7 small fishes + 1 large fish on my shopping list, but I am wondering if I should add another 1 red and 1 purple firefish.

Does anyone has any other opinion?