Volo's class is a mess, I was also shocked to find out he wasn't a bard. BG3 certainly tried to depict him as one.
About Alfira: I think it's pretty obvious the Patch 7 teaser is talking about being able to have her momentarily join you before she um, moves to a nice farm upstate, because she joins you after you've clicked the Long Rest button, I'm pretty sure. So you can't really do anything with her in terms of real combat. It's just there as a gag, perhaps to trick new players into thinking she's really joined you so there's more impact to... her slipping on a banana peel.
I'm about 99% confident that's the extent of it. Nothing for non-durges. Wonder if they've recorded voicelines for her spells, or if you can re-spec her with Withers and such.
It probably also applies to the Dragonborn bard lady, but to the same very limited extent.
