Tack “&udm=14” on to the end of a normal search, and you’ll be booted into the clean 10 blue links interface. While Google might not let you set this as a default, if you have a way to automatically edit the Google search URL, you can create your own defaults.
Uh… The settings for AI Chat and DuckAssist are both on by default when you use DuckDuckGo. You can see them in Settings -> AI Features