My laptop has been running at close to 100C for around 4 years now (i7 2630QM - heavy rendering, not 24/7), almost throttling, but not throttling. And even if it was throttling, that's all it would do, no harm to anything whatsoever, I have a cooling pad, but I don't really use it, as long as it's not throttling, it's ok in my book, can't care less. It did shutdown once, at 107C if I remember correctly.
However, Intel don't agree with that, as the TJMax is supposed to be 100C, but not all chips are created equal. Software doesn't really tell us the whole truth, anyways enough of my story, I'll end with my PC is still running strong. If your components are throttling, then yes, it does affect performance, because the component(s) are basically slowing down, in order to maintain heat, and if that doesn't work, it will know it, and you will be left with a PC that shuts itself off, with no warning. This isn't going to harm your PC in any way, it's just a way for components to protect themselves from damage.
Hopefully that answers your question!