My only personal experience with three or more long term companions is Thirteen's initial crew, which compels me to say; no more than two please.

A group (this includes the Doctor) of two, three or four is ideal IMO. Four and you sometimes have the issue of finding something for them all to do. Two and you sometimes have the issue of turning them into a double-act. I know Moffat said he always preferred the dynamic of a trio, but I couldn't find much evidence of that in his writing. Three would probably be my vote too though.

I'm not sure the wording of your options is very clear. "A duo" suggests the Doctor is one of them, which would be the same as your first option.

My favorite eras happen to include 2-3 companions. It allows for more varied personal interactions, instead of just Doctor+companion.

I’d say 2-3 companions is my preference, but the writing has to be up to it. Chibnall would’ve benefited more from having just Yaz, I reckon.

This feels more memorable...

Good luck keeping up the quality while trying to keep a good dynamic between 9+ people.

I think 1-2 is probably best, depending on what sort of stories are being told.

@FH2104, why not just follow some other superhero shows and stuff? Ones with multiple protagonists.

@TheCritic&RobloxMaster21, you know it.

Though sometimes, I wonder if maybe we should have an incarnation who doesn't have any need for friends at all. Seeing about the god revelation three years ago...

@Kevin 'Chalky' Kaiba Kevin, the god revelation you are referring to did not happen. The Doctor's ability to regenerate is completely unchanged from how it was before that episode was broadcast.

The idea of a companion-less Doctor might be doable, although I think it would wear thin pretty quickly. As much as it's excellent, Heaven Sent does feel a bit endless to me, and four episodes was more than enough for The Deadly Assassin. But doable isn't the same as worth doing. The reason the companion is there is to be our eyes and ears in the Doctor's world. If we don't have any, there's really no point watching. The 2008/09 specials came perilously close to proving that—there was no "companion", but there was a companion-like character in each, with varying degrees of success.

@Kevin 'Chalky' Kaiba It's also pretty firmly established throughout the modern series both by telling and showing that it's not really good for The Doctor as a person to be companionless for an extended period. So while there could be a show about that, I think it would have to be a very different vibe.