Just like the filtration, lighting is going to be more of a dictate of what you plan on doing. If you are doing to want plants needing med-high light then you will need better lighting. But the more lighting you use then you get into other things like CO2
With today's lighting it is harder to use the wpg
rule. T5HO lights put out more light so would be higher than a normal T5 ot T8. I do think 2.5 -3 should be good for many plants and not have to get into CO2
or ferts or anything.