RCA - Revenue Cycle Analytics - This refers both to RCE and the various Analyzers.
RCM - Revenue Cycle Model - This is inside the main MLM tool. It does not require RCE, but it is more useful if you have RCE. The Model lets you build a model of your funnel with Stages and Transitions. This is needed in order for Marketo to understand your funnel metrics and how to calculate this. This data goes into RCE and the Success Path Analyzer.
Success Path Analyzer - This is a tool in MLM that only works if you turn on RCM with your Lifecycle. It only shows the green success path. Pretty useful, but RCE is more detailed.
Opportunity Analyzer - This is intended to show Sales that their Opportunity indeed had marketing influence because it shows all the Interesting Moments and Program Success points for the Contact Role and any related Contacts on the Opp's Account.