That mode is baked into several games,I have not seen a campaign explicitly created to use your first variation of troupe style, with a single stable from which all players can pull.
It's a subset of Ars Magica 1-3, which also includes rotational GMing; without the rotation it's the default for 4th.
The minor characters are group assets in Star Trek Adventures, with a player sans character suitable for scene being able to grab one of the junior officers. (If grabbed in multiple adventures, the minor characters grow.
The game that defined "Troupe Style Play," Ars Magica, defined it with these key featuresMaybe but I think you see a rotating GM seat a lot more often than you see troupe style play.
- Only the GM plays more than 1 character at a time
- Each player owned 2 characters
- The group had a bunch of shared minor characters for use as alternate PCs
- GMing rotated.
The other groups I was in contact with playing Ars Magica did likewise.