ASHRAE Loads in OpenStudio
Can Open Studio calculate ASHRAE loads?
If your question is, can OpenStudio apply ASHRAE 90.1-20xx assumptions to a model, then the answer is yes. Take a look at this repo. The thing you probably want is the baseline automation measure, which hasn't been published to the building component library yet, but should be very soon.
OpenStudio doesn't perform any physics calculations itself; it uses EnergyPlus for that. And, yes, EnergyPlus uses the heat balance method.
Look at the HVAC Sizing Summary table under EnergyPlus results.
The OpenStudio standard report also has peak load summary plots.
Which loads? Outdoor air? Plug loads? Lighting loads? Please be more specific in your question.