Thank you. Yes you are right the entire character will be larger than screen. However in After Effects a common trick to reuse a character (especially with only a few loops, like walking) is the camera would zoom and focus on each part of the character back and forth, so effectively only about half of the character will be on screen.
The usual video export size is 1920x1080, therefore I make sure to have at least the upper half of the character with about 1000px height so it wouldn't pixelate when I zoom in. In total, the height would usually be about 2000px if it is human. (Maybe needs to be more than that if I am planning to cut in a close-up eye shot of an animation loop, which is quite common)
Last year I have an animation project which my friend made the music and I draw/made the video. The walking girl character was exported from Spine to AE. I use the aforementioned zooming tricks to reuse the walk loop as much as possible. (Although the resolution is not as large as described)
VIDEO
