I do a lot of work in a black-box with flexable seating.
We ALWAYS secure at least 3-4 chairs together in a row (usually most of the row) and we NEVER use folding chairs. Our chairs are stackable on their rolling racks 18 high and are stored in a rehearsal
hall (or elsewhere in the building) when not needed. In the normal seating configuration in the Hexagonal room we have 8 levels of risers each (with a row on the floor) with a 1' rise (and 6" steps), which allows for 147 chairs. We commonly transition to a neat in-the-round configuration where we can get upwards of 160 chairs (more if we want, depends on staging) or
Cabaret seating for anywhere from 60 to 110.
We have minimal light codes and codes that actually dictate that chairs be connected or secured if there are so many (can't recall the code rules for the life of me).
In the standard configuration the sides of the risers are against walls on 3 sides, but there are railings on the stair units going up the sides, which we custom-bolted to the risers.
In
arena or in-the-round we add side and back railings as needed along with a
chair rail (toeboard), all made from steel.
We light the
house effectively from above, changing with the seating configuration, however we have permanent lighting for our standard configuration.
Our seating risers were replaced a few years ago, and it is fully custom not only due to the shape of the room (company actually had to rebuild several risers to make it fit correctly) but also due to our chosen rise of 1' per row.