That is how you go about it, but it depends on a few things. If the headset is USB, then it will work fine regardless whether or not Realtek software is installed. Also applies if the two devices are connected to different audio sources. Let's say USB and onboard audio, or a sound card and onboard audio. If both devices (analogue speakers and analogue headset) are connected to onboard audio, then rear and front separate output needs to be enabled in the Realtek software, otherwise you get the same audio from rear and front connections. If you set Windows default to the onboard audio, then set onboard audio in VOIP, it's still the same output. When separate rear and front outputs are enabled, the option appears in sound devices as a second Realtek output.
If the OP has a USB headset, then it's as you described. If he/she has analogue headset, then Realtek software is required in order to make it work.