Let's say I have two Alpha models which I add to my algorithm using a Composite Alpha Model. As the OnSecuritiesChanged Function is triggered every time there is a change in my universe do each of the OnSecuritiesChanged Function in my alphas update after each universe selection?

If so, do they run concurrently or in the order which I add them to the Composite Alpha Model? Also, if I were to execute code that would remove old equities from the universe, rebalance my holdings, etc. (Basically nonessential code in terms of producing insights) in OnSecuritiesChanged would I need this code in both functions, or would one of the functions overwrite the other?