That is a nice looking tank.
1. I would think the one filter will be sufficient. They say to clean them every couple of weeks or they become a nitrate factory. So far I have had no trouble with mine but I am looking to change over to a HOB
overflow and a sump in the near future.
2. I like peaceful tanks myself. You also want to make sure that all the fish you select are reef safe if you are going to add corals down the road. In my 45 which is about 3.5 months old I went with a Kole Yellow Eye (I know I will need to upgrade the tank or find him a new home in a year or so), a pair of clowns, 6 line wrasse, 3 blue/green chromis, fire shrimp, 3 emerald crab and a CUC. I really like the mix of fish and the constant movement they give.
3. I think you will need another power head before you start adding coral though.
Keep the pictures coming. I want to see this come together.