micro grow you may be better off with just 5000k bulbs.
reason saying this it very hard to cool 2700k bulbs in small areas.
5000k will give you a bit of blue and red spectrum.
lastly start with 2700k plant will be much more stretchy than if using 5000k not to desirable in a micro grow.
yo naturalorganic figure up lumen/watt on any bulb see which are most efficient.
other factors play into this also how many fixture can you use? how your growing plant lst or straight tree?
tree needs much more side lighting than lst/scrog. efficiency is not always the answer.
figure out your style of grow and what you can cool figure out what works for you.
efficiency
18w = 1000 lumens/18w= 55lumens/watt
23w = 1600 lumens/23w= 70lumens/watt
42w = 2700 lumens/42w= 64lumens/watt
105w = ~7000lumens/105w=67lumens/watt
200w = 12000lumens/200w=60lumens/watt.
link to my cfl grow any questions feel free.