Cryptsetup and partitions
Solution 1:
You may ignore it. sdc and sdd are block devices, so you can encrypt them or build file systems on them the same as sdb1.
Partitioning adds flexibility or course. But you can also get that by adding the disks to an LVM storage pool.
Note, I'm not able to immediately find any documentation about this. So take it with a grain of salt. But it's always been my understanding, and I've used unpartitioned disks without any trouble.