Safe Search and Privacy Safeguard are optional. It's really a personal preference -- I don't use them.
Safe Search is an additional search environment. If you do a search using Norton Safe Search, the search will be performed by Ask.com. The results will be processed by Symantec code and a search result page will be generated flagging known unsafe web sites. Optionally the unsafe sites can be deleted and not shown. However, paid sponsered links remain even if unsafe.
Like most sites, Ask.com collects information as described in their posted privacy policy. Ask.com may share this information with third party content and sponsored links providers. Ask.com has a feature called AskEraser to delete your search activity. However, AskEraser only removes that information from its own servers. It cannot delete information that has already been shared. It can take up to 24 hours to remove. All that Privacy Safeguard does is enable AskEraser.
There is another similar sounding NIS 2012 feature that you should turn on -- Safe Surfing. If you click on the Advanced button in NIS 2012, you will see some Web Protection settings. Be sure the Safe Surfing option is ON. Turning this option ON enables the AntiPhishing and Safe web features. Web Norton Safe Web is a reputation service that analyzes Web sites to see how they will affect you and your computer. This provides the information that enables the identification of unsafe sites for Safe Search. However, unlike Safe Search, the unsafe site flags will be embedded in the results from your regular search site. Google and Bing are supported, I'm not sure who else. It works in IE and Firefox.