As for the bulbs I would say 2 actinics and then the others are going to be personal preference. I'm using 10k white. Some would go with a white and blue or some may go for two blue.
Depending on the coral you may or may not need to dose calcium. If you are going to have clams then yes, probably, same with the hard coral. I don't have experience with either so can't really advise.
The overflow is going to be connected to the sump. I don't have any links to DIY overflows handy but you can probably find some by searching. Make sure it has a siphon break to avoid flooding. If you DIY you can figure out the GPH
by having it empty into a bucket and timing it... like a 5g bucket that you have marked off to say how much makes 1g, 2g, etc. Time it to see how long it takes to fill 1g, 2g, etc and then you can calculate the GPH
. If you buy one it should tell you what it is rated at.
I thing you are looking for somewhere in the 10x tank volume for the GPH
on the overflow. If it is 10x then you would want a 550 GPH