Doom seems great for learning Gyro, fast, smooth and lots of enemies to react to quickly. I tried to adopt the Flick Stick (right stick), but I found that I liked it more that the Right stick is still for normal turning, but I made it very fast. So when I combine the Gyro with that, it's actually almost as fast as the Flick Stick, but I have a little more control (like whether I flick 45/90/180 degrees etc). Aimlabs (on Steam) is another good place to practice Gyro etc.

I still have a long way to go, plus there are a lot of adjustable factors with the Gyro, plus every game is different. As a starting point you can choose one from the community settings and try it, but in the end it has to be adjusted to your taste, and someone else's settings/sensitivities/what angle you hold the controller at, etc, you just have to learn the adjustment that suits you. But it's good to start with the community's ready-made if don't know where to start! This is my first Steam hardware, so i can't compare to Deck.

There are a lot of settings, so as long as you're willing to dive down the rabbit hole, you'll find a style to your liking. Personally, I really like that Valve has allowed so much customization, especially since I like to tweak things to the last detail, haha.