Thats a loaded question lol , I'll keep it basic and short as I can, first we used hydro for what it was, The race car of growing, once we had clones ready for veg, meaning past the clone stage ready to grow, we pushed them for the fastest growth we could get , we also pushed then through transition and stretch to get the most out of them, why ,we we're growing 5 -6 -7 foot plants in very short amount of time, short growth time, big plants , big yields , shit tonne of lights so we didn't screw around, and before someone says it , fast growth less time does not = reduced quality , 1 thing I will say though is i think a lot of the older strains especially the heavy indica ones could hand more nutes then a lot of the stuff today.
I'm going to disagree with you about C02 directly related to nutes, there is 9 cardinal factors to growing #1 and most important is sun/light and all other 8 factors fall in line with the amount and or intensity of light. ex. if your running 600umolsm2s your other 8 factors will have to be with the parameters of that amount of light to produce optimal photosynthesis. at that amount of light those parameters are some what wide, now if your running 1000umolsm2s which is fairly high light those 8 factors need to be run in a much more precise measurement to the amount of light and to each other to have optimal photosynthesis. which is harder to do as light intensity goes up. here is how I break down the 9 factors 1 is light, 2,3,4and 5 are your above ground factors .Temp RH wind/air flow and C02 the 6,7,8,and 9 are the below ground factors Temp,water, nutes and 02. So when running high light photosynthesis etc is only going to be as good as how optimized those 8 factors are. the needed C02 would be more directly linked to the amount of light needed for photosynthesis. Nutes/ water are more directly related to the amount of light, under high amounts of light the plants needs / will uptake higher amounts of water, which means nute levels should be run lower.etc to better understand all this I'd suggest to research photosynthesis, all the process and factors around it, but also research up the stomata and how it works ,especially the guard cells that swell and contract to open and close the stomata , once one has a great understanding of these process, it much easier to understand or see why humidity, leaf temp or wind/air flow is so important, ( VPD) the same as O2,water, nutes and temp of the soil etc. how these all work together and the higher the light the more precise they need to be optimal growth / photosynthesis etc.