which configurations are more optimal from a 6x1Tb raid, 2x3Tb or 3x2Tb
Here you have missed an important, in my opinion, the moment capacity of the first embodiment will be 5ТБ (RAID5), the second - 4TB (also 5), the third - 3TB (RAID1).
storing films with the possibility to easily adding disks
This will require the controller, as well as some no, but skills. We regularly bring data recovery RAID arrays after the incorrect rebuild.
Well, RAID1, of course, drives you can add is that for greater reliability.