Troupe style play

[aramis erak]

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.

That mode is baked into several games,
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.

Maybe but I think you see a rotating GM seat a lot more often than you see troupe style play.

The game that defined "Troupe Style Play," Ars Magica, defined it with these key features

• 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.

It didn't define whether or not NPCs were owned by various players for their GMing, but my groups all did: each of us had some NPCs that were "off limits" to others.
The other groups I was in contact with playing Ars Magica did likewise.