Tank size is only a reserve! The tank helps buffer the tool usage vs the pump output. Ideally the pump should be able to supply enough air to run the tool all be its self. Many manufactures rate their compressors by Hp and by amps or by cfm. Cfm is also misleading as this is just bore by stroke displacement. It doesn't take into account the efficiency of the unit or more accurately the inefficiency of the unit. Years ago I was taught to rate by the CFFM the free (available at the pump head) volume of air. Sadly no two manufacturers will standardize the rating systems.

The compressor you have described should cover most of your needs.