Consider in the simplest case with two disjoint quorums
B. If something comes to a consensus in
B get the update as well?
On a high level view, does each peer on the Stellar network maintain the same global ledger?
Yes, all nodes maintain the exact same ledger as a replicated state machine on top of the Stellar Consensus Protocol (SCP). It is a serious configuration error to have two disjoint quorums--such a configuration will cause serious problems for the network if the two quorums agree on different sets of transactions for a ledger. At that point people will have to decide that one side or the other was misconfigured (probably the more recently added nodes should have configured their quorum slices to depend on existing nodes).