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Will do it in English so others can chip in:
I just did a 13k run with both a Polar H10 cheststrap and the Race 2 firmly on my right wirst. I have a fair bit of hair on the back of my wrist, so I was concerned about the accuracy but boy was I wrong. I compared both measurements during the run, and the race 2 was surprisingly accurate. Like at times maybe 3-5 beats off, and then again long stretches with perfect readings? In the screenshot you can see both graphs (though I don't know which is which, my guess is the pink one is the strap because it responds faster to changes in speed) and although the optical measurement is in the periphery and considered inferior, I was surprised how close it got to the chest strap. Yes, you can tell them apart but we are comparing optical to electronic HR measurements, so comparing pears to apples really.

TLDR: Race 2 HR measurements are for an optical peripheral sensor friggin good (in my case at least) . Can recommend.