Hello

According to this https://harlerunner.de/optische-h... test report, it should now be possible to pair the Polar OH1 with Garmin watches, subject to restrictions (see article).

Since I don't know the GARMIN products, I unfortunately can't answer the question.
However, I assume that this will not work. Every manufacturer wants to sell their own products.
I used to wear a chest strap with the usual sensors from Polar that measure the "pulse current".
Since my recorded heart curve was very irregular and the pulse was usually very high, and my GP suspected a technical problem, I bought this product which uses a different measuring method. "Light sensors". However, the image of the heart curve remained the same. After a long time, the cardiologist found the problem: Ventricular fibrillation (cardiac arrhythmia).
Advantage: The OH1 is much more comfortable to wear, e.g. on the upper arm.

I also use the heart rate monitor with a Suunto Spartan Trainer Wrist HR GPS, which works well,
I have no experience with Garmin.