This is probably one of those "how long is a piece of string?" questions but my personal definiton of a small layout as one that a sole modeller can transport on their own to an exhibition or meet in a normal sized car along with stock and control gear (and ideally a second operator( then set up and operate on their own if necessary)
My own H0 layout is 5ft 3ins long on a tapered board that folds horizontally to form a box. A simple fiddle yard plugs into one end and it represents a small French terminus on a short line.?
In the UK there is more of an emphasis on complete layouts - usually fed by a "fiddle yard"- and modules are far less popular.?
If you're a US modeller and want to know more about this then it's worth watching Kathy Millatt's two videos on the subject
https://www.kathymillatt.co.uk/blog/2017/10/19/anatomy-of-an-exhibition-layout/
Kathy is a British NMRA Master Modeller whose how-to videos are really good. These videos are based on a clinic she gave at one of the NMRA annual convention. Kathry is currently one of the judges on a British prime time TV series in which, in each episode, three? teams of modellers compete to build a complete layout in three working days, programme six will be the grand final . After two episodes the series is proving remarkably popular, gives due respect to the many artisic? and craft skills involved, and looks set to give a real boost to the hobby here.
