Bitcoin Security Protocol for large corporations

Hey guys,

I was wondering: Do we know what kind of security protocols large corporations apply to their bitcoin holdings. Obviously, this information will not be made public but can we speculate/do we have information? Obviously they likely use Multisig but are there other protocols? For instance I could imagine something like a "need to know" basis, where no one knows all the key holders. I would imagine something like, let's say 4-out-of-6 MultiSig where A only knows that B and C hold keys, while B only knows D and E hold keys and so on.

How do companies like Coinbase handle this where they have to frequently sign transactions!? I cannot imagine every single TX has to be multi signed. I would love to get your input what we know about how they handle security and transaction frequency.