Filevault

Depends on the machine and OS. On machines which support AES-NI (Sandy Bridge and newer) you should use FileVault. On all other machines AES-128 encrypted sparse disk images (create them with Disk Utility) are the better choice. AES-256 is much slower, and easier to crack than AES-128.

http://www.schneier.com/blog/archives/2009/07/another_new_aes.html

 

That means Early-2011 and newer hardware.

Yes. SB is the 2nd generation of the Core i3, i5 and i7 processors.