Questions regarding disk format
You can install Yosemite on an encrypted partition. To use encryption, you also have to use core storage. If you do not use encryption, then the use of core storage is optional. If you encrypt after installing without core storage, then a conversion to core storage will take place. Fusion drives require the use of core storage. Yosemite can only be installed on a partition that is case insensitive. Personally, I have avoided using core storage. I do not see any advantages to using it unless you have to.