Perhaps you could narrow things down a bit by trying to figure out what key characteristics need to drive your design. I'm in aerospace. Some of the systems I stare at are designed pretty much exclusively based on safety considerations. Others are almost completely devoid of such considerations and more care is given to maintainability due to expected high rate of change, or requirements on throughput etc. Security is another joker with a high potential of impact on design. Also figure out what you consider to be "system design" as opposed to "software design".