Can the following be achieved via configuration of control variables in the out-of-the-box Lifecycle Manager...

No. Specifying which applications support new account requests is not normally achieved by changing control variables in the out-of-the-box LCM workflows. That behavior is driven by application configuration, provisioning support, account creation policies, schemas, QuickLink configuration, and requestability settings. LCM workflow control variables influence how an already-launched workflow behaves: approval handling, policy checking, provisioning behavior, notifications, foreground/background behavior, trace/debug options, and similar execution controls. They do not define whether an application itself supports account creation. For an application to support new-account requests, the application must support provisioning, have the relevant create-account capability/configuration, and expose the request path through LCM/QuickLink settings. Putting this into workflow control variables would be the wrong design layer. References/topics: IdentityIQ Engineer — LCM workflows, control variables, application provisioning configuration, Create Account policy, Manage Accounts/Manage User Access.