If I come across a fabric that has both pattern I and pattern II available, do I need to buy samples for both?

It’s the same fabric, so one sample is enough. The difference is how the pattern is turned (as pictured). So for flat faux shade valances as an example, pattern I valances are available from 18″ to 52″ wide, while pattern II valances in the same fabric are available from 18″ to 120″ wide.