I would see the Parts as Kits as in MD and MNM
A Part contains the settings(parameters and effects) and the samples assigned to each track + 16 scenes configuration. There are 4 Parts in each bank. So you need to spread out the usage of parts within a bank.
When I first started, I used first part for the first 4 patterns, second part for the second 4 patterns and so on. After some practice I realized that you can achieve a lot of things with parameter locks and this greatly enhances how to make the most out of parts