The wall panels themselves are made of wood - plywood, OSB and construction wooden beams. All treated for fire protection. Unlike plasterboard these panels do not crumble, so they can be de-assembled and re-assembled again multiple times.

There are also always some decoration materials on top of that - which ones depend on the theme, the room and certain details of the project.

You can jump on the ceiling with full force, no joke, it will have no effect on the structure. Leaning on the walls/pushing them also has zero effect.

The whole structure has multiple points of interconnection, so it's each panel helps to hold it's neighbors and the ceiling.

Well, it does depend on the country a lot (sometimes even depends on a certain city). But there is good chance you can process it as a temporarily construction - like a tradefair booth.

It's also way more acceptable for the majority of landlords - knowing any changes to the floorplan can be easily removed (and knowing you are interested to remove them in case of relocation).

Flat floor and power outlet (220v or 110v, depending on where are you located).

Yes, it is. In certain countries certain fire marshals may have a no-ceiling policy for indoor structures - in that case the room can be provided with floor and diagonal beams to substitute the ceiling.

All wall and ceiling panels include the soundproof insulation inside. It's not record-studio level, let's be honest, but it gets the job done. It works best being combined with thoughtful sound design (that's on us), and reasonable game schedule.

No need for huge gaps between games, just making sure you don't get a several groups stacked in the lobby at the same moment.