Khanh, I'm not an expert on light or coral, but I do know enough to be dangerous! I'm sorry for the long reply, but I don't want to assume you know this stuff, so I'll try to cover even the basics.
There is a lot to learn about light, leds fixtures, how your corals use light and what effects the light has on everything else in your tank.
First, let's clear up the misconception of getting to 100% power. You'll need to figure out what the maximum amount of power your systems need to use to get the right amount of light in your tank.
1) The easy way is to do that is with a PAR meter which measures Photosynthetically Active Radiation, or the light that ALL plants use in the process of doing photosynthesis. But most people don't have PAR meters and they are kind of expensive and not very useful once you get your light set properly. Some people borrow them from other reefers or rent them from an LFS.
2) Find somebody who has the same fixture you have and is successful with keeping coral in a tank similar to yours. That's possible here with all of us, but given your fixtures are not the most common ones in use, it may prove difficult to find. I'd recommend you try asking in the Lighting, Filtration.... Forum (
http://www.reefcentral.com/forums/forumdisplay.php?f=212 ). Tell people what led fixture you have, about your tank size, what kinds of corals you want to keep and you may find help.
3) I call this the 'Canary in the Coalmine' approach which is what I was refering to with the start using low power setting and ramping them up over time. I'd set 1 or 2 inexpensive frags as high up in your tank as you expect any corals to be. These are the 'canary' corals. As you raise you power levels over time, you will get to a point where 1 or both of those corals will start to get too much light and bleach. That will almost always be before you get to 100%. When you see one of those corals start to bleach, back the power levels down 5% or 10% and you should be good to leave it there.
Your other question was about why so much blue light?
Let's start with your coral. The coral is an animal and living inside the coral polyps are a form of plant/algae called zooxanthellae. This algae does photosynthesis that feeds both the algae inside the coral and also the coral itself. The particular kinds of zooxanthellae that live in coral use mostly blue light (400nm to 480nm wavelength) to do this photosynthesis. Your coral could almost survive on light that is mostly blue. The white light is a mix of a wide spectrum of colors like red, green & blue (RGB) and your corals use some of those other colors to produce pigments that create some of the color you see in your coral along with some proteins and other chemicals they need to survive. But they don't need nearly as much white light as they need blue. So more blue and not as much white is good for the coral.
The light in your tank will also be used to grow other nuisance algae (which you don't seem to have yet). These nuisance algaes do their photosynthesis mostly with red light which is part of the wide range of colors included in the white light. So white light can help glow algae that you don't want. So less white is OK for your corals as long as they get some and less white also helps keep nuisance algae from growing. Some people even go so far as to cover the red leds in their fixture. This can help if you are getting an algae bloom you don't want.
The other component we need to consider is your eyes and what you want to see when you look at the tank? Some people like a very blue tank and some hate it. Others like a cool white look which is a lot of blue and some white. Others like a warm white look that is more white and less blue. Even this is OK as long as you realize that it is less useful to the coral and more useful for nuisance algae. You get to control how blue or how white your tank is with the dimmers. So set them to a level you like to look at. Just remember it only takes a little bit of white light to make the blue look go away to our eyes. But the blue is still there and the corals don't see the light with our eyes.
That is the basics as I understand them. There are a lot of articles about light and how corals use light. And if you have questions, I encourage you to ask them. That's how we all learn.