I can't get a clear answer on this I see "Concurrency Limit" and "Max Concurrency Limit" on integrations: Does Concurrency Limit assigned to an integration remove that available concurrency limit for others? Say we have a limit of 25, if I assign 6 to integration A, then do Integration B and C only share the remaining 19? Or can they use more if A is not using it at the time?

If you do that, you are assuming you can allocate the resources better than the hub. implementing a router equivalent of QOS. If you let the system do it, it will oversubscribe the processors more effectively IME,