[CentOS] LVM vs Physical Disk Encryption

I have a couple of question about Disk Encryption during an OS install. I want to setup encryption on a system where I might have to enlarge the LVM's by either adding another disk or by enlarging the disk size at a later date. This is a VMware VM so just increasing the size of an individual disk is pretty simple and then expanding the LVM on it.

Should I use LVM or just Physical Disk Encryption? What are the benefits and drawbacks of them? Should I do both? In setting this up for the first time, I did both. Will that slow down the system because it is actually encrypting everything twice? If using LVM encryption and I add another drive to the LVM is it automatically encrypted?

Thank You Steve