Stats: macOS 10.13 (High Sierra), Core i5 (I5-4258U) 2.4 GHz w/2 cores and 64 bit architecture, 8GB DDR3L SDRAM, Iris 5100 video card

This never happens with default Clothing. It always happens after I've been playing for a half an hour or so. Suddenly it's like my sim has a hole through the middle or through their ankles and long streaks of black or skin color shoot out across the screen like rays. Sometimes if I pause and start moving the screen to try for a screenshot they just disappear. I've had trouble getting a decent image of this but I might be able to attach one later. Should I be worried about my CC, my video card, or some setting I haven't thought of? Does anyone know why this is happening?

LOD's. level of detail. you could delete the specific cc. it does happen a lot.

Does it mean the level of detail in the CC is too high for my mac?

Try to check-off some of those possibliies first...

1. Your Graphics settings could be set too low.
2. Your Graphics Chip could be showing you early signs of failure or even overheating.
3. Your Drivers are not up to date.
4. Your Computer isn't up to top notch to handle the demands of a game like this.