Use the three slots as a visual conversation
Two speakers
Start with one character on the left and one on the right. That arrangement gives the frame a readable exchange and leaves the center available for the background’s depth cue. Make the current speaker slightly larger or more central when the line needs emphasis, then reverse the treatment for the reply.
One speaker and one witness
A visible character does not need to speak. Place a supporting figure at a smaller scale or farther from the center, keep the dialogue nameplate on the active speaker, and let the witness shape the scene without competing for the line.
Three-character test
Enable the third slot when the composition needs a club group, a reaction shot, or a foreground interruption. Three full-size sprites can quickly fill a 16:9 frame, so use scale and side choices to create a clear front-to-back relationship.
Expression comparison
Keep the background and dialogue constant while changing only expression A, B, C, or D. The visual difference becomes easier to judge when the framing remains stable. This is faster than inspecting isolated image files and guessing how an expression will read inside a scene.