I've read a number of books about Space Marines. So, they're supposed to be not just warriors, and not just superhumans, but the equivalent of knights in the 40K universe. In the fiction some of of the chapters seem to be like the rest of the 40K Imperium, even a bit worse - we're incredible, superior to anyone .who needs our assistant. The only people who matter, really, are other Space Marines. Doing horrific things to normal people, not even able to speak civilly to anyone under them. Others seem more like the idealized Arthurian knights - they're abilities just give them greater responsibility - they're knightly when the speak to even civilians, and while they will do things that hurt normal people, their goal is to protect them and avoid that where possible.
The general problem for all space marines seems to be Hubris/Pride - any of these chapters can end up making bad decisions because of it.
So, is this correct? Do behaviroal standards just differ by chapter, or are some chapter just unable to comply with standards, or are the nobler chapters heretical?
I'm curious - is there a World-of-Darkness like mechanic for their Hubris? That is, to do cool stuff, they have to become more prideful, but as they do so they're gradually becoming more monsterous, where they're randomly capturing citizens and turning them into servitors.
Thank you in advance for your assistance.