NotSoSecure have made this wiki for cloud security, with tools and methods for how to research and develop knowledge in this topic. I find it quite useful when browsing various cloud security research blogs they refer to, tools and methods. E.g., for AWS a lot of defensive and offensive tools are listed such as ScoutSuite in which I have great experience with.
Minimum Viable Security Product has a baseline requirements list for B2B software and products thats worth checking out. It is founded on the same principle as most frameworks, e.g., as the CIS critical security controls, by “prioritizing security functions that are effective”.
MS Threat modeling tool, Cairis, Iriusrisk, Kenna, OWASP pytm, OWASP threat dragon, threagile are some of the most known threat modeling tools I know.
Personally I like OWASP Threat Dragon for being supported on most common platforms, and because of its flexibility in designing and registering threats. MS Threat modeling tool provides a lot of out-of-the-box threat scenarios with details based on the model designed.