This is a question that crossed me as well and was further discussed here: Throttle processing power/bandwidth to keep stable FPS during loading
In the end it depends on your use case. I’m seperating what should be loaded in the beginning behind a loading screen and what can be loaded on the fly. When models are small and optimized there is almost no stutter on load.
I think the biggest issue is the texture loading. That’s why I first load my models with compressed textures and then add the normal textures while the user can look at the models.
If that won’t work for your use case a worker thread might be something to look into.