Proudly American
Copy the three dimensions that answer different questions
For each exact model, record its listed viewing area, framing opening and appliance depth using the manufacturer specification sheet. Then check the chosen decorative front. A bezel can change how the edge of the view reads in the room. Heat & Glo's Mezzo and its traditional 6K/8K series publish model-specific dimensions; compare the exact variant rather than photographs resized to the same width on a screen.
Compare full-size outlines with the appliance off
Use two paper outlines on a separate wall or board, away from a functioning fireplace, and mark the finished hearth and viewing height. Sit in the usual chair and stand at the room entrance. A very wide but shallow view has a different relationship to furniture from a taller rectangle even if their listed widths appear close. Keep decorative trim outside the marked glass area so it does not inflate the comparison.
Hand the installer a preference and an installation question
Record which outline you prefer and why, then ask the installer to assess the wall depth, venting and required clearances for that product. The room mockup can settle proportion. Only the manufacturer drawings and site conditions can settle whether that proportion can be built at the chosen height.