Apple Watch fitness and health apps

Please read the link I gave and the rest if my answer.

Watch

• Workout app to record
• Activity app to summarize

iPhone

• Health app for detail of the data
• Fitness app to summarize

Any analysis apps will read the Health app data but zi have never needed one

I can hardly believe you have had Apple Watch all those years.

Apple Watch has neither Health nor Fitness apps (they are iphone apps)

Watch has the Workout and Activity apps which strongly correlate to the fitbit activity tracking.

The main difference is probably no live step counting.

Check out this article for Using Workout basic information 

Use the Workout app on your Apple Watch - Apple Support 

 In general there are two types of workout:

Ones using gps distance, time, heart beat, age, weight, height, gender. 

And ones using time, heart beat, age, weight, height, gender but without distance.

Some like swimming can detect types of stroke but in general they estimate effort in calories and time for your build snd the types of workout help you keep track of what workout types you did.

I doubt if yoga and taichi and weight training give different effort results if the time and heart rate are the same.