Every plate currently in the layout comes in together, staggered the way the design has them.
The bottom logo bar. Independent of the plates — either can be on air on its own.
Plates stay evenly spaced whatever the count. Names you type into hidden slots are kept, so going 3 → 1 → 3 does not lose them.
Add as a Browser source at 1920×1080. The background is transparent — the camera feeds go underneath it.
Companion: use a Generic HTTP action with GET and one of the URLs above. They do exactly what these buttons do.