While I am still evaluating UNRAID, can someone advise me on how I should configure my drives. I have a dell R730XD. I am booting off of the internal usb. I have 2 480Gb ssd in the rear caddies. I have 24 1.2Tb SAS 10k drives in the front backplane. I am unsure how to best use the drives for parity, cache, and storage. I plan on a few docker containers for home automation etc.. and a iCloud backup. Then basic storage for our files. 

For the disks it depends on your performance needs, assuming nothing special, I would use the disks in the array with dual parity and create a zfs mirror for the SSDs

One recommendation I would make (from previous personal experience) would be to just add the minimum amount of disks (plus maybe 10% extra) that provide the level of storage you currently need.  It's easy enough to add additional disks to expand the unRAID Array later on whereas emptying then clearing (zeroing) disks can take some time and needs care to ensure you empty/wipe/remove the correct disk(s)!