real-time protection turned on for both? Also, is it ok to have two antivirus programs, one running real-time protection and the other for manual scanning?

yes you can have both real time tools running at same time.anti virus= can have as many as you like. but don't ever have more than one turned on at same time. I have 3. I use one running all time and then scan with the other 2 every now and then to see that the first one is doing its job. hope this clears this up for you.

Windows Defender's realtime protection takes the form of a resident-background scanner for spyware, similar to that of a traditional antivirus program. Spybot uses two different methods for realtime protection - the immunization function, which is passive, blocking known threats by blocking those threats from activating through your browser. The active protection within Spybot is Tea Timer, an extremely simple activity monitor that is more invasive than UAC on Vista. It's really a question of how much protection you feel you need, and at what expense compared to usability.