If you want to look at actual container security best practices, check out CIS [1] & DISA [2], and NSA [3], with some theory at NIST [4], as well as the documentation from your preferred cloud vendors, be it AWS, Azure, GCP, or other, as well as the specific container security practices.
[1] https://www.cisecurity.org/
[2] https://public.cyber.mil/stigs/downloads/
[3] https://media.defense.gov/2021/Aug/03/2002820425/-1/-1/0/CTR...
[4] https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.S...