Light spectrum during veg and bloom periods

there are differenecs, but it's always relative to genetics.. there's no spectrum you can give a naturally lanky difficult to branch out plant into a small bush... in fact it'll still be a lanky sativa-like structure even if you give the "best" light for increased axillary growth. So, worry less about that and more about DLI. you want to be giving upwards of 40DLI to your plants - wither 12 hours or 18 hours - or - over 1m^2 or 3m^2. The amount of umol/s of light you provide is far greater concern than your spectrum at this point, especially given most grow lights fall in a small CCT range and similar SFDs. the amount you give per day is proportional to hours of use. Since you have an autoflower you don't have to worry about that. Also, since you don't have to drop to 12/12 light cycle, you don't need to find 50% more light than what you were able to give before (assumes same area of coverage), which means you can cover 50% more area with your light over 18hours vs 12, but you also run it 50% longer. it doesn't save watts.. just can provide a bit less per hour over the course of a day.