yes you're being paranoid, I'm also prone to migraines and if anything, ANC soothes me as it sound like muffled calm white noise, so unless that bothers you to some extend, I don't think you should worry too much.

ANC is actually super helpful for migraines

ANC cancels out noise, not add it. Research what phasing does.
I've used Galaxy Buds Pro (1st Gen) to get some peace and quiet in the Bus every morning, in-between screaming children, the loud engine noise, etc. Works really well.

What added audio? ANC doesn't add anything.I understand you read how ANC works and got scared of it. I can assure you that there is nothing unnatural or unusual in this process. Sounds cancel other sounds all the time. When you speak, your voice bounces off other things and people and gets partially cancelled. When a guitar plays, it cancells some of it's own frequencies, which is why it has it's characteristic timbre. Cancellation means being quieter just like absorption or isolation. If you have a positive pressure and a negative pressure in the same space, they cancel out and you're left with no change in pressure. Just peaceful silence with no side effects.

Think of it this way - if it's getting colder, but you turn on heating, you have constant temperature. It's exactly the same with ANC, except the change is happening very fast. Since 'you turn the heater on and off' just as fast, the temperature is constant and your room cosy. Sound works in the same way, just instead of heat, there are tiny changes in pressure. ANC keeps the pressure constant and on the same level as outside the headphones. To your ears it's very relaxing.

I also get migraines.

I have a pair of Sony wh-1000xm3 and still get migraines from them. In this case it's the pressure of the headband on my head combined with the added air pressure from the ANC that triggers migraines for me. I tried to remove the headband compression from the equation and tried some Air Pod Pro (gen 2), however, the ANC is still uncomfortable for me.

I'm currently using some Aful Performer 5 (paired with a Fiio UTWS5) and liking them so far. They're really comfortable and have great passive noise isolation. They also sound great too.

Previously I misunderstood how the cancellation process happen and thought it happened after the sound reached the ear. Thanks for the enlightenment!

Thanks! You reminded me of lectures of signal processing I attended some time ago, never thought of it!

They also have DSP but that's a different technology

The pressure from the noise cancelling in my Sony WH-1000XM3's can sometimes aggravate a headache.

I have found that, depending on what I am doing, I will use either the ANC headphones or IEMs with foam tips for passive, or Emu-Teaks, which are Semi-Open and very comfortable for me.

I recently picked up some Air Pods Pro 2s and haven't had the same issue with their ANC implementation as I did with the Sony's.

Interesting... I guess it is good to test headphones out extensively while they can be returned to the seller. Thanks!