nibus

Hello, I am about to build an unRaid system and have some questions regarding adding drives to an existing array. Because of budget, up until now I have just bought HD's one or two at a time. By now I have around 12 drives, ranging from 2-3TB each. The problem is, most of these are mostly full and formatted to NTFS. However I believe I can free up 3 drives to start an unRaid server with. I would like to create this 3 disk array, and then one by one copy the data from my other NTFS formatted disks to the array, and then add each disk to the array as I go, expanding the array and eliminating all of my single drives. I assume this is possible, but I do not know if I would run into any problems with adding 7-8 drives to an array one at a time like this. I also assume this would take a long time, but I don't know exactly how long it takes to add a drive to an existing array. I'm not sure which distro unRaid uses but I assume it could mount an NTFS volume? When the build is complete I will have about 12 drives, running on two SUPERMICRO AOC-SASLP-MV8's like is recommended in the wiki. I also had one more question - is it better to run these controllers in PCIe x4 slots only, instead of x16 slots? I plan on using an Intel i3 processor and haven't found any boards that have 2 x4 slots. Thanks for your help!