Yes, GLES3 will export to html.

Unless you are specifically targeting mobile devices in the web browser GLES3 should be fine. If you are concerned about compatibility you can certainly use GLES2, just be aware there are certain limitations. You will need to use CpuParticles2D rather than Particles2D, that kind of thing.

Here’s Godot’s official docs concerning the differences. https://docs.godotengine.org/en/stable/tutorials/rendering/gles2_gles3_differences.html?highlight=gles2