GWs event parameter estimation posterior

Hello.
I have some questions about the h5 datasets files that I found in LIGO documentation
Regarding the parameter estimation posterior events of the released datasets, what is the essential difference between a Cosmos datatype and a non-Cosmos datatype?

What datasets are usually used in research, and how do I know which model analysis to use for each event?

What are the crucial points about the event datasets for events falling in the lower mass gap?

Thank you!