I been working with unreal for a few years now. Right now my strong point is level design over the blueprints. And like Ashern said just jump in. If you have something in mind they making it. If you can get any asset packs from the market try those. If you want to make something custom then yes you will have to start using another program. 3DS is spendy and I’m not sure on Maya. But you can also use Blender 3D. It’s free and does what the other 2 can. As to making a scene it’s usually best to start with the terrain if making an outside scene or make the building for an indoor scene. And adjust the lighting as needed.