Cloud/data protection
The app that connects to the watch can only be used if you create an account in the cloud. The data is apparently stored locally and transferred to the cloud at the same time. The data protection conditions in Garmin's T&Cs allow Garmin to do pretty much anything with the personal data. This can neither be prohibited nor differentiated. If you don't accept the terms and conditions, you don't get an account, without an account you can't use the app, without an app the watch is simply a watch and therefore far too expensive, and as a sports watch it is certainly useless.

Offline Usage
If the smartphone to which the watch is connected does not have internet access, the app and thus all configuration and setting options cannot be used. In short. Not usable offline.

My conclusion: I won't buy one of these. I don't spend money to be forced to give all the data I collect to Garmin for free. I want full control over my data and there is no other reason for Garmin to store my data in the cloud other than to get my data.

I can't say anything about the calorie measurement, it doesn't interest me. I can say that the oxygen saturation measurement is totally useless - the values are much too low, and a cheap measuring device from China (price: less than 5 francs) that you put over your fingertip is very likely to measure much more accurately. However, this does not provide continuous measurements. My guess is that all oxygen measurements from watches are almost useless, I don't assume that other manufacturers provide much better values.