Hi,
From SEP 12.1 all three features are supported on all the Windows operating systems.
Symantec recommends to use all three features i.e. Virus & Spyware, Proactive Threat Protection (PTP), Network Threat Protection (NTP) on client OS.
While installing on Server operating systems customer should take a call.
Refer this article in that case.
Best Practices for Installing Symantec Endpoint Protection (SEP) on Windows Servers
http://www.symantec.com/docs/TECH92440
There are many new enhancement have been made in SEP 12.1.
Check this article
Few differences between SEP 11.x and SEP 12.1 EE
https://www-secure.symantec.com/connect/articles/feature-differences-between-sep-11x-and-sep-121