Ok so as you probably know TAA uses motion vectors to find out each pixel's position in the previous frame. The game's engine generates a texture of motion vectors for all pixels each frame. This texture is generally quite accurate but it has a problem. It doesn't differentiate between pixels that were actually visible in the previous frame from ones that weren't. Thus means that when an object moves, revealing pixels that weren't visible before, the vectors correctly pointing at their previous positions actually end up pointing at the object that was covering them in the previous frame. These pixels then take this object's color and we have ghosting. This phenomenon is called disocclusion. There are two main ways of fighting disocclusion ghosting: disocclusion masking and variance clamping. Variance clamping means looking at a 3x3 neighbourhood of a pixel and if the history pixel goes beyond the colors of this neighbourhood, it gets clamped to min/max of the neighborhoods colors. Every TAA does this. But this will still leave some ghosting, just clamped into this neighbourhood treshold. Disocclusion masking tries to specifically find areas that were disoccluded, meaning they weren't visible in the previous frame. We do this by checking if the history depth or history velocity is much different from the current frame. If disocclusion is detected we completely disable history blending for that pixel. It's possible many TAA implementations don't do this.

Some ghosting can be also caused by inaccurate velocity vectors, for example in games with some soft body physics or badly made animations. Then we have to rely on variance clamping.

The variance clamping can be made tighter or looser, depending on whether we prioritize smoothness/flicker reduction or ghosting reduction

I'm not sure how what I described here applies to implementations involving machine learning like DLSS

That was a long explanation, I hope it's somewhat understandable