Hi, welcome to the forum.
If you want to display some text in a WebXR scene, you don’t need to create a 3D geometry in the first place, did you check out this example ? This would reduce the number of polygons and help a bit, but it still produces meshes, and creating meshes every frame always lead to performance issues.
The best thing would be to pre-create the characters meshes, and only show/hide them with their
visible property and position them to create new words.
This will help, but if your text is big, it’s still a lot of independent meshes, which is still a problem for performance. The solution is to use InstancedMesh, so you only have one mesh per character, visually duplicated by the GPU.
Be sure to check out this library to create WebXR user interfaces., it was created to address this kind of problem.