Animation in Photoshop Too Slow!

I am an illustrator for 20 years, but I have begun to animate in Photoshop lately. I am new to the animation timeline and don't know all the tricks. I've brought in large jpeg images as objects, which need to be a great deal larger than the 1280x720px aspect ratio because I am zooming into a tiny part of them. The Photoshop file itself is over 2GB so it is being saved as .psb file. The size is so large now that Photoshop is too slow for me to use it effectively. What's the best way for me to handle this issue? I am only at 20 second for a 1.40 second animation project. I need to find a better solution?

1. Should I render the video and then import it into a new Photoshop file as I continue adding to it? I'm guessing the file size will be terrible.

2. Should I render the animation in pieces and then import it to iMovie and fade the pieces together? I have iMovie, but I don't really know its capabilities.

3. Should I purchase Adobe Animate? I have never used this application either, so I don't know its capabilities.

Thanks for any insights!

Laura