Here's a recent-ish thread on the topic.
As per the title? If you could give a brief explanation of the app/s you suggest, and how they “improve” your life/workflow I’d be grateful. Thanks in advance.
forums.macrumors.com
TLDR: kinda depends on what apps you have on the phone that have a companion Watch app and what you will use the Watch for.
At minimum, setup some watch faces. Setup Apple Pay for the Watch. With iOS 15, maybe setup the Fitness Focus for when you start a Workout via the Watch. Or an Automation for certain Workouts (eg. I have one for when I start a hike Workout, starts a GPS tracking app on the phone). Setup the Dock on the Watch with the apps most important to you and maybe not in a complication in a watch face. Maybe an Automation to change the Watch face (eg. I have an Automation to set the face to a "workout" watch face I have before my workout time, then switch to a more stylish one when done with a Workout).
For me, the most used things on the Watch are Workouts, Timer, audio controller, Apple Pay, Weather. And second screen to the phone to get Notifications.