When you use script type="module" you don’t need to use window.addEventListener( 'load', init ) - the script is automatically deferred.
Regarding the render quality, try setting up a PMREM (type of environment map). See this example for details: three.js examples
Apply VRayMat materials
I haven’t used the Babylonjs exporter. But are you sure that it exports this type of material correctly? It’s usually best to use the built-in 3DS Max materials when prepping a model for export. Same for Vray lights - anything fancy you do with these lights/materials cannot be supported in three.js and probably won’t even export. Just use normal targeted point/spot/direct lights, or set up the lights in three.js.
The exception is if you’re using the lights to bake texture maps. But it may be harder to match the baked maps well to the lighting setup within three.js. Some experimentation is required here to figure out a good workflow.
For adding dimensions, do you mean as annotations? See my example here, and the rest of this thread: