It looks like BitNinja already has it’s own built-in security. Seems similar to “managed” hosting types of packages where the website security is already included in the package. I have no idea whether the security that BitNinja provides is everything that you need. Maybe do some research, check reviews, etc. to see if you need any additional security.
As far as whether or not there would be any conflicts with BPS security and BitNinja security I don’t really have an answer for that question. If you decide to purchase BPS Pro and it is not compatible with BitNinja then I do offer a 30 day money back guarantee. You may not need BPS at all if BitNinja has good security. Sorry I can’t answer your questions with any specifics. Just don’t have any experience with BitNinja.