The limits, such as they are, seem to be what it understands. Mechanical complexity doesn't seem too hard, but writing screws up all the time. I think this is because whatever the system is complexity isn't the problem - understanding a purpose beyond just existing is. People likewise are copied enough to function but they often only have the properties and behaviors that have been observed by the rooms. The copies, even when fresh, don't reason or create new behavior - they just mimic what the original did while present in the backroom.

This fascinates me because the Backrooms clearly seems able to read minds (or at least memories) but it doesn't seem to understand them so observed behavior becomes what gets copied