Which system service apps could I disable to protect my privacy
Root the phone, you won't regret it. Unless you're on Verizon of course. Verizon hates modders and security enthusiasts.

The spyware apps you definitely want to get rid of are RootPA, Silentlogger, DT Ignite, and Carrier IQ (man, I hate those bastards.)

The rest is just bloatware for special features (ANT+ for S-Health, T-mobile/Verizon's ringtone apps, freemium services for watching movies, music, etc)

I forgot, since you have Samsung, there is a way to disable system apps without rooting. It's called Package Disabler Pro - Google Play and it only works on unrooted Samsung devices (some kind of device loophole per se). You can disable any system app from there that Settings.apk won't allow.

You can also use a VPN firewall without root, such as this one, to protect sensitive data from ever getting out there. Otherwise root and use DroidWall, more secure, doesn't rely on a third party VPN.