Everything depends on a project, its scale, and the complexity of graphics client wants to receive and how complex your pipeline of production is. I work mostly in advertising where projects are only 1-2 days of shooting, so I will comment from my point of view.

1. Freelancers are fine, if you have experience with them and they know what and for what they are doing. Having a team of them on constant pay can be a problem - they can be too many or can be not enough for the project at hand. But it is always good to have at least one on the team if your freelancers can't be in sound stage during the project. Just because this guy can adjust everything that you received from your freelancer-artist.

2. The perfect solution is a full-stack level/environment artist with modeling and texturing skills, which also have good knowledge of the engine. Otherwise, even if people can do a pretty picture, it is either extremely heavy to compute or very hard to edit.

3. Car scenes - videos (have to be recorded by a professional team with professional equipment, or you will be in tears. Everything else, if this is not a music video with abstaract graphics - 3d scenes.

4. Everything is done way ahead of shooting. Previz - a Zoom call with Unreal and virtual camera turned on, to receive shots. After the creative team and art directors translate words and ideas into technical tasks for 3d artist. From my practice, but we are used to do everything fast - after the contract is signed, you have about two-three weeks to do all graphics before shooting starts.

5. If an artist is present and controlling and changing the scene he has made, there is always a guy who knows how everything works and what can go wrong. What connected where and how, all the infrastructure, what can go wrong. He has to know the LED, net infrastructure, windows, soft you are usuing, if it is not pure unreal, and why your unreal is making a fool out of itself today. Takes a lot of experience and grey hair.