mod_security has SecFilter and SecRules that are individual security filters and rules so typically you can just modify those, BUT if your Host is applying mod_security overall to all sites on a particular Server and not compartmentalizing or virtualizing hosting accounts ie vhosts then they would most likely decide not to alter/edit the SecFilter/SecRules.
In my personal and professional opinion I think that mod_security has some nice features, but since you can actually achieve much better control and security of your personal website/hosting account security rules and filters by using BPS Pro then mod_security is not really necessary in your case.
For folks who do not have BPS Pro or any other security measures installed on their website, mod_security would of course provide general security for their websites. What is important to remember is that Host’s have to configure Server level stuff like mod_security to work for all website types. ie php based websites, html based websites, etc. For that reason typically Host Server level configurations must be designed/configured generally to work for all site types overall.
So to answer your question. BPS Pro actually adds more security protection to your website then mod_security can offer due to the fact that Host’s must configure this in a general and not a specific way to ensure it works for all site types. You have complete control of your personal Hosting Account/website security filters, rules, etc. by using BPS Pro