Infrastructure as a Service (IaaS) is the deployment model that will best meet the requirements of retaining control over the operating systems, patches, and settings of all resources. IaaS provides the cloud infrastructure but leaves the management of the operating system and applications to the user.
Reference: The cloud service models and the level of control they offer are fundamental topics in the CompTIA Cloud+ certification material.

Clustering refers to the use of multiple servers/computers to form what appears to be a single system. This concept is key for achieving high availability and resilience, especially for latency-sensitive workloads. By distributing the workload across a cluster that spans multiple regions, the system can continue to operate even if one or more nodes fail, thus maintaining performance and availability. Reference: CompTIA Cloud+ Guide to Cloud Computing (ISBN: 978-1-64274-282-2)

The Reserved resources model offers cost savings for committed use over a long term, which can reduce costs while maintaining performance for predictable workloads. The Spot instance model allows users to take advantage of unused capacity at lower prices, offering significant cost savings, though with the possibility of instances being terminated when demand rises. Both models can be strategically used to optimize costs without compromising performance.

To prevent proprietary code from being exposed to third parties, a cloud engineer should use private repositories for the containers. Private repositories ensure that access to container images is restricted and controlled, unlike public repositories where images are accessible to anyone.
Reference: The concept of using private repositories for protecting proprietary code is part of cloud security best practices, which is covered under the Governance, Risk, Compliance, and Security domain of the CompTIA Cloud+ certification.

Containers are the best compute resources to optimize cloud resources and lower the overhead caused by managing multiple operating systems. Containers encapsulate applications and their dependencies into a single executable package, running on a shared OS kernel, which reduces the need for separate operating systems for each application and simplifies resource management.
Reference: CompTIA Cloud+ materials discuss management and technical operations in cloud environments, including the use of containers to improve resource utilization and operational efficiency by minimizing the overhead associated with traditional VMs.