Sure, I understand, hope you get a effective solution for the vision you have!
Just in case I will drop a few library names and tips, even if not for yourself might help others.
Sprite sheet/s are better than image sequences
GSAP scrolltrigger is your best bet for scroll animation.
Break your animation into stages, where someone could pause. Use scroll snapping for these locations.
Start loading assets asap. Use a custom load function to get assets async without blocking render.
Avoid relative movement or change of shape for 3d objects, bake lighting when possible
Only sharing this to help anyone. I am not available for web-dev at the moment. Connect with me if anything I have shared is interesting or anyone needs help.
