AjaxSettingCreating is an event on RadAjaxPanel (the base class RadAjaxControl) and from documentation it looks like those events can be hooked to interact with the underlying UpdatePanel.
I am not using RadAjaxManager for two reasons, one is that it seems more suited to the panel and two I had hoped for a fairly simple migration from UpdatePanel.
RE: documentation. I have been reading quite extensively on RadAjaxPanel and RadAjaxManager and to be honest I have yet to find a really in-depth article that goes "under-the-hood" on the Telerik Ajax suite.
Would be great if you could address the original question on parity of the UpdatePanel and RadAjaxPanel.