We compared smart ring heart rate data with smartwatches, and the results may surprise you (...Instead, it's the Amazfit Helio Ring that won the hardware accuracy contest. And since Amazfit recently discounted it to $199 and made its pricey subscriptions free, the Helio Ring has become more appealing.
On the other hand, the Helio Ring has unresolved problems like the limited number of sizes (three), short battery life (four days), and lack of automatic workout detection.) https://www.androidcentral.com/wearables/smart-ring-hr-accuracy-test