Hi @mynameismyname (mine too, BTW!), welcome to the forum!!
Here is my take on getting started with WebXR -
Get started with Babylon and understand its features. understand the toolkit you have, what’s possible, what’s not. Understand what the render loop is, how meshes are imported, how the GUI works and how to use ES6 modules to keep your package size as small as possible. Understand PBR, sprites, particles systems. And then add a call to the WebXR experience helper.
WebXR is another way to interact with your user. it has its own view/camera(s), different user input, some interesting terminology, but all in all - when referring to VR in the browser, it is just a screen and a gamepad (generally speaking ) and not more. Under the hood, Babylon’s WebXR implementation is using Babylon to display the scene. This is why understand the framework is much more important (IMO) than understanding XR.
It might take some time to get it to work. Using the WebXR emulator is a nice way to start. An Oculus quest is a wonderful device to test your scenes on. So is a windows MR device. Other devices can still be a bit unstable.
This is the technical side of things. Just as you don’t learn WebGL to use babylon.js (you can! of course, but WebGL calls are all abstracted for you, so you don’t HAVE to), you don’t need to “learn” WebXR. It is recommended, of course, to know the difference between local-floor, unbounded and viewer mode, to know what immersive-vr mode means, to know what an input source does. But you wouldn’t need it to get started. It is all abstracted for you. This is the difference between learning WebXR and using WebXR with Babylon.js
On the UX side of things - this is where it gets interesting. As VR/XR/MR/Whatever is a different way of interacting with the user, you will need to find new ways for the user to interact with the scene. Many different ways can already be found in the wild. Some like the users to move freely, some use teleport. Some add HUD elements, some have the information floating in the background, and some put it as a wristwatch on your “faked” hand. The possibilities are endless, and babylon is here to help on the technical side of things
Carl has already provided with some of the docs pages, and they are a good starting point. If you have any questions, directly about webxr or about babylon, the community and the team do their best to answer them as quick as possible.