Apart from the Apple Watch (which became a door stopper when I moved back to Android) I’ve not had a lot of success with really good accuracy on watches. I actually opted to get a Polar H10 chest strap, and it is really super accurate. I usually live monitor the data on the Polar app on my phone (and it uploads to Strava, and then to Samsung Health), or if I’m outside I pair my Samsung Galaxy Watch to it with the Sporty Go! app so it shows on my watch.