Hi again Brett,
SilkUI (like OutSystemsUI) is a library with dozens of Patterns avaible, for both Mobile and Web. You can see them right here: https://silkui.outsystems.com/Patterns.aspx
As you can see, it has several Mobile and Web Patterns.
If you're referring about these Web Patterns, then yes, they are a part of SilkUI.
This means that if you remove SilkUI and install OutSystemsUI, you need to replace these usages to the corresponding OutSystemsUI Patterns.
You can see available OutSystemsUI Patterns in here: https://outsystemsui.outsystems.com/OutSystemsUIWebsite/PatternOverview
Hope that this helps you.
Kind regards,
Rui Barradas