threejs-loaders

Use GLTFLoader from three/addons/loaders/GLTFLoader.js and call loader.load with the model URL and a callback. The callback receives a gltf object whose scene property you add to your scene, and whose animations array can be played with AnimationMixer.

Create a THREE.LoadingManager and pass it to each loader's constructor. Set manager.onProgress to receive loaded and total counts for a progress bar, and manager.onLoad to detect when all assets finish loading.

Yes, GLTFLoader supports Draco compression through DRACOLoader. Create a DRACOLoader, set its decoder path to the Draco decoder files, call preload, then attach it with gltfLoader.setDRACOLoader before loading the compressed model.

Load the HDR file with RGBELoader, then either set its mapping to EquirectangularReflectionMapping and assign it to scene.environment, or pass it through PMREMGenerator.fromEquirectangular for prefiltered PBR environment lighting.

The texture color space is likely wrong. Set texture.colorSpace to THREE.SRGBColorSpace for color and albedo maps, and use linear color space for data maps like normal or roughness textures, then set needsUpdate to true.

Loaders use callbacks, but you can wrap loader.load in a Promise that resolves on success and rejects on error. This enables async/await syntax and Promise.all for loading multiple assets concurrently.