WordPress is inherently quite secure software, because of open source, extremely wide installation base and reasonably fast security updates.
There is no such thing as security plugin that magically increases security, while causing no conflicts. Security plugins either act to monitor situation and inform you after the fact (important, but it’s not prevention measure) or restrict what can be done to reduce possible attack vectors.
It is most important to make sure all code running is well maintained and audited for security issues and no security plugins are replacement for that.