Traditional animation of large objects / backgrounds / many small objects?

I was just wondering what the best way to animate large objects / many small objects / and backgrounds would be. I know there are limits to how large a sprite sheet can be, and there are texture size limits. Here are some example use cases, maybe someone can explain the best way to handle each.

Use Case 1 - Background
I have a background where 1/4 of the screen is a swimming pool. I want to use traditional animation to make the water churn and swimmers swim. Should I be using the animator for this with very large sprite sheets? Should I use video player? Should I use something else?

Use Case 2 - 100 Candles
I have ~100 candles in the background of one scene. Do I need 100 animators? Is there another more suitable technique? I know animators have overhead so I don't want to bog down the game for little background touches. What's the best practice here?

Use Case 3 - Spirits
There's one scene in my game where a bunch of spirits are swirling around in the background. This is the same question as #1 basically.

Please let me know if there are any recommendations/best practices I should be bringing to bare.

 

Anybody?

 

Case 1
This is now my main question. I'm not sure how to handle this. Should it be a video with a sprite mask? What if I need to have some alpha in there?

Case 2
So for Case 2, I just realized you can use one animator to animate multiple sprite renderers at once. No big deal. That will cut down the animator overhead dramatically.

Case 3
I think I can use Sprite Atlases for this one. The spirits will expand and contract so hopefully only a few frames are big. That said, it could be that our animators will make the sprites swirl around the whole screen in which case I still have no idea how to handle that. Does the whole background need to be a video?

 

Anyone have advice for Case 1?

 

Bump