Flowxpress tool is a mickey mouse version of flow simulation. In short,. your options are very limited in xpress tools (all of them). Hence, to perform detailed analysis you should consider using the full module.
To address your second question: CFD is computational fluid dynamics. Let's simplify: CFD is the technical term for numerical fluid flow and heat transfer analysis (I know this one doesn't sound that much non-technical ).
This may also be helpful on the stress analysis side: https://forum.solidworks.com/message/687274#comment-687274
Hope it shades some light for you. If you have more questions, do not hesitate to shoot.
Thank you for your reply and will be ready with few more new questions.. Thank you again