Use Output:Table:SummaryReports with the HVACSizingSummary and ComponentSizingSummary keys (or just use AllSummary) and OutputControl:Table:Style, HTML;and you'll get it in the HTML

You can also use

Output:SQLite,
  SimpleAndTabular;                       !- Option Type

And you can query the ComponentSizes table.

FYI, openstudio has handy methods on every object that has an autosizable fields, where if you associated a sql file to your model, you can just call a method and it'll give you the autosized value.

For example, for a CoilCoolingDXSingleSpeed, you have a autosizedRatedAirFlowRate() method.

You can also do Model::applySizingValues and every autosized field will be replaced by the calculated autosized value.