Yes, you can go back to your settings after creating a people list. You can even edit your search settings by clicking on the "Imported Profiles" column > Sources > Last Search, which will show you a blue "Edit Source" button. However, please note that if you make changes to the search settings, it will only affect new results - any previously imported results will remain unchanged and you would need to manually delete old data if desired.
Source:Find People [Clay 101] - Clay University