We have a nice labeling system in this plugin for most of the features. Features that are labelled "Advanced" can break your site. Those are there for the *really advanced* users.
Don't activate the features that are categorized as advanced unless you know what you are doing. There are plenty of basic and intermediate features that you can use and get very very good security protection/coverage.
If you have activated an advanced feature and it broke your site then do the following:
Step 1) Deactivate the plugin using this instruction:
Step 2) Reset your htaccess file using this instruction:
You should be good after that.