Troupe play is play with each player having more than one character, serving different roles. There are several ways to structure Troupe play - and each is best suited for a different play style.
The Mission Impossible Troupe
The players each have one character in play at any given time, but the group leader selects the particular characters, one from each player, used in this session or story arc from two to three characters offered from each player. The characters should be different types, but roughly equivalent skill level. The name comes from the old Mission Impossible TV show, where the MI leader - Mr. Phelps - would look through the currently available agents and select ones suited to the particular mission at hand. On the TV show, of course, the ones selected were almost always the same, but allowed for selection of particular guest stars. In principle, however, the method enabled the group leader to select an optimal selection of skill sets, and it is this principle that should be followed. it is best used where the PCs are all members of some larger organization, and are all specialists.
The Tri-level Troupe
The players each make three characters ‐ perhaps an older character with lots of skills, a mid‐level character with moderate skills, and a young character with few skills. Another form would be officers, NCOs, and grunts. Groups can be mixed ‐ with varying levels of competence ‐ or matched ‐ with everyone more or less equivalent. This form allows a more hierarchical model, with one or two main characters who lead the others, a couple secondary characters, and the balance as low level cannon fodder, which is great for side-quests, detached parties, and any othe simultaneous play, where two things are happening at the same time.
The Teacher/Trainee Troupe
A player or the GM makes one older, experienced character, the Teacher. The rest
of the troupe are Trainees, just learning their craft, whatever it is. The Teacher leads the groups in learning situations, which can be canned training courses a la the Danger Room, or low risk real life situations. Of course, risks can be deceptive, and a low risk situation can go bad fast. this is a great model for some supers groups - X-Men type supers schools, junior members of a Justice League or Legion of Supers organization, or even sidekicks. It also lends itself to a Harry Potter type wizard school.
The Classic Troupe
This is the form taken by Ars Magica, where PCs played a Wizard and a skilled warrior Companion each, and the relatively unskilled Grogs were played by whoever wanted to play them. The players make two characters each ‐ perhaps a spell‐casting type and a competent warrior type. They also make a group of less combat-skilled types, such as young trainee warriors. Each competent warrior is paired with a spell‐caster played by a different player, and the trainee warriors are miscellaneously played by anyone who wants to as an additional character. This can also be the setup for games where the different groups are different intelligent species, such as riders and dragons, or pilots and intelligent star fighters/mecha. The less-combat skilled types can be attending the dragons, or mechanics for the mecha.
The Battle Troupe
Each player makes a group commander, and the other players each make a character to serve under each leader. This is great for military games, where command is distributed, and small groups are working as parts of a larger whole - such as crews of small military starships, or tank crews, or the officers of a Submarine wolfpack. Each unit functions as a separate whole, yet working together with other units for a single mission or purpose.