Loading in IF can be interesting sometimes. It takes some planning and a lot of tweaking to make a large presentation work snappy.
Maybe another IF staff member can back me up on this…but in my experience, IF will load things first when the scene is entered, then when assets are “shown” inside that scene.
When entering a scene, you can trigger a “loading” screen if you need to buy a few seconds to let the scene load. Then, with the assets themselves, you can be strategic about pushing them offscreen, reducing opacity, sending them backward in the layer list…or combinations of those. This means they will be loaded immediately with the scene and ready to be shown. Also, I believe the web browser asset has triggers for when content is loaded, which can allow you to design other UI elements until the web page comes up.
That’s usually what I do - but just like anything, there’s always some problem solving we need to do when it comes to how much should be loaded into a scene, and how much should be hidden or simply invisible within it.
Hope that helps a little.