OK, for analog audio, it doesn't make a pile of beans difference what you use as long as the cable is adequately shielded. The frequencies involved are too low for the cable to function as a transmission line at practical lengths. So, you don't need to worry about maintaining a characteristic impedance like 75 ohms.
For digital audio, or analog video, the connection is designed to function as a 75 ohm transmission line. Ideally, the cable and connectors should maintain this characteristic impedance their entire length. That means using 75 ohm coax, which RG6QS is an example, and connectors. Unfortunately, there is no such thing as a 75 ohm RCA connector. Has to do with geometry and dielectric constants. The best you can do is to use something that comes as close as possible, like Canare's "75 ohm" RCA connector. But frankly, impedance mismatch for the short distance of the connector is likely to have no effect whatsoever that you will be able to detect by listening or viewing.
For digital audio, or analog video, if the cable is less than a significant fraction of a wave length long, you can treat it just like the audio cable. Ever seen the cheap, short RGB/audio cables supplied with some devices? They work just fine.
RG6QS is not a good choice for any of these applications. It is designed for something else. And it is stiff and difficult to work with. A good choice might be something like a good RG59 with a stranded copper center conductor for flexibility (definitely not copper plated steel) and 95% copper braid. 100% foil shield in addition to the braid would be a step up. One of the miniature coaxes might be the best way to go. But it will be more difficult to find the connectors.