I would suggest starting as simple as possible. You’ve dipped your toe into a number of different packages. You’ve seen 2D and full 3D packages. Sounds like some of your stories are based on animals and some may require people. Decide on what basic look you want and how far you want to get into it. You can create everything and do all hand key framing of characters if you want or you can try to focus on the storytelling and try to use as much off the shelf as possible.
If you’re just making animations Unreal is fairly easy because you can ignore all the game and program logic for your needs. Create a basic scene in Unreal and put in your characters>
Look in the Unreal Marketplace free tab in the Unreal Launcher. If you can get a free scene or at least free props all the better.
Select Sequencer in Unreal and start positioning at different frames in the timeline.
You can use a control rig but good complex animation can take time. The other option is to download or buy mocap motion that you can apply to your characters.