Eh? What's the difference between option one and two?
As far as loading light with Alliant powders, I've used Red Dot and Blue Dot. I have, and continue, to load a lot of light (lead 185gr, 8x57 ca 2,000fps) rifle loads with Blue Dot. I suppose I chose Red Dot, over Green Dot, because if I'm going fast powder then Red is faster than Green; and, if I'm going slower 'fast' powder then I chose Blue Dot over Green Dot, because Blue is slower than Green. I don't see any reason why Green Dot wouldn't work as well as Red Dot. The thing Red Dot has going for it is that "The Load" is out there.
The above paragraph is me saying "I don't know, I don't have any experience with Green Dot in .223". That said, at one point in the murky past I made up a spreadsheet with 'presumably' safe loads for pistol powders in rifle. I could PM/email that to you. I wouldn't want to post that in a forum, because somebody reading that might assume that it's actually a safe, or tested, or recommended load, because it certainly isn't.