storage will depend on how much space and speed you need for your projects/media. small bitrate files like h264, won't need as much space or speed, like setup 1. large bitrate files, and larger frame size (4k+) will need more space and speed, like setup 2. if you don't use AE disk cache or premiere preview renders, the internal ssd of the imac may be fine to use as the cache drive for premiere and not have to purchase the samsung usb ssd.
the owc enclosure seems to be software raid. so you could configure all 4 drives as raid-0, or only 2 or 3 drives as raid-0 and leave one or two for backup. or replace some drives with ssd's then use those left over hdd's for shelf backups or for transferring projects/media with others.
there is this other thunderbolt drive system that appears to have built in hardware raid. if doing raid 5, this would be handy.
Thanks. HD or 4k workflows and codecs will definetly be important here, and I will mostly work in HD. Maybe some 4k from GH4 (mp4) and Sony FS5 (xavc long gop), but mostly in HD timeline as of now.
Reading some reviews it seemes like the OWC software raid sollution is delivering very good performance, but I will check out the Promise Pegasus sollution, seemes a little pricier though.
If any of you have good or bad experiences with iMac setups, please share