This is in line with what my thought process was. The light intensity in veg isn't nearly as important. I just flipped to flower so run it at 100% going forward at 12 inches? I'm not using any supplemental C02. I don't need pull lbs. or anything crazy as it's just me and 2 others so if I could avg out to say 2 or 3 oz per month I'd be more than satisfied.
In VEG, the main goal is maintaining strong light for healthy growth. Too little light leads to weak spindly branches. For flowering, high PAR light is crucial for big buds and decent yields. CO2 is vital; I use sealed grows with ductless AC for consistent 70-80°F. Running out of propane slows growth in c3 plants, they can take up to 1600 ppm with ease so why not provide it?
Using LP or NG burning for CO2 is efficient; mushroom methods don't raise CO2 enough. A small 2-burner setup works for small spaces with AC.
You should know as well, not using co2 would be like if you got a supercar that has half power with normal gas but full power with race fuel. Your running a supercar on normal gas rn at half power without co2 also you're actually being less efficient with your resources because your burning the same amount of electricity without reaping the benefits of all that par due to lack of elevated Co2.
This is assuming you live in a normal 400-450 ppm co2 zone and dont have a pack of dogs living in your grow room or just adjacent to it.
My vote: Save money on light dimmers/controllers and run co2, run lowest possible lighting in veg and blast them in flower. Keep co2 levels around 1200-1500 ppm when lights are on for optimal light and plant performance.