For example Carlsen is currently the world number 1 and favourite to win a match against any other player in the world. Is he also favoured to win a match against Caruana + Mamedyarov + Ding Liren acting in consultation? How much stronger would a team of top GMs be compared to a single GM?
If it matters: standard classical time controls (shorter time controls makes it hard to consult teammates after all), the team of GMs are side-by-side, and they're playing electronically with the opponent in another room (so opponent cannot eavesdrop on their conversation). The team know each other and prepare in advance, and so does their opponent.
Edit: since the question is closed I'm editing the answer I found into the question before I forget about it or lose the source.
Q: Could a team of us [British GMs] beat Magnus?
A: We stand a much better chance. I mean just in terms of spotting tactics or spotting ideas. But somebody would need to be the boss somehow with good clear idea of what needs to be done because obviously if you've got completely different people it could get confusing. But I do think that the team would have a better chance than individually - absolutely.
So the answer is yes a team of GMs is stronger, although we don't know by how much.