Hello,
Go to Manage Extensions page, click the Content extension, expand the Meta Tags parameters group, and disable keywords and description generation. You will probably need to delete the already created URLs and clear the cache so they can be recreated without the JoomSEF's metadata.
The Active checkbox is used when there are two or more same SEF URLs for different Real URLs - in that case, you can set which of the Real URLs will be used.
What exactly do you mean by "unwanted URLs"? Can you post some examples?
Best regards,
ARTIO Support Team