Question about timeline

Check under the "Control & Physics 1" tab before replacing the character. It's possible that the original character's Scale was reduced from the default 1.0 value. That or your tall character has a higher value, in either case it's possible you could fix the animation by just making sure your character is the same scale as the original.

There's also a "body scale" and "height" slider in the base morphs you can use to adjust the height. The other way is faster but depending on how the characters are placed in the scene (or something like that I can't seem to think atm) the model alignment can be thrown off. Turn off the model collider before you adjust to.

The scale is always a problem, and character replacement is always a problem. Especially with "precise" situations like your finger animation.

The base character scale is one thing IF the original model is not morphed with height modifying morphs. This is a problem with character swapping: everyone approaches the height management differently.

This is something you can't fix magically. Even with the "ApparenceSwapper" contained in VAMStory.
Modifying character on the fly requires you to potentially edit the animation as much as if you were animating it yourself in some scenarios.