The server installation method that would optimize server resources is core. Core is a minimal installation option that is available for some operating systems, such as Windows Server and Linux. Core installs only the essential components and features of the operating system, without any graphical user interface (GUI) or other unnecessary services or applications. Core reduces the disk footprint, memory usage, CPU consumption, and attack surface of the server, making it more efficient and secure. Core can be managed remotely using command-line tools, PowerShell, or GUI tools.

The most efficient subnet mask for a point-to-point heartbeat connection between two servers using IP addressing is /30. A /30 subnet mask has 255.255.255.252 as its decimal representation and
11111111.11111111.11111111.11111100 as its binary representation. This means that there are only two bits available for the host portion of the IP address, which allows for four possible combinations: 00, 01, 10, and
11. However, the first and the last combinations are reserved for the network address and the broadcast address, respectively. Therefore, only two IP addresses are usable for the point-to-point connection, which is the minimum required for such a link. A /30 subnet mask is also known as a point-to-point prefix because it is commonly used for point-to-point links between routers or servers1.
A /28 subnet mask has 255.255.255.240 as its decimal representation and
11111111.11111111.11111111.11110000 as its binary representation. This means that there are four bits available for the host portion of the IP address, which allows for 16 possible combinations. However, two of them are reserved for the network address and the broadcast address, respectively. Therefore, 14 IP addresses are usable for the subnet, which is more than needed for a point-to-point connection and would result in wasted addresses.
A /29 subnet mask has 255.255.255.248 as its decimal representation and
11111111.11111111.11111111.11111000 as its binary representation. This means that there are three bits available for the host portion of the IP address, which allows for eight possible combinations. However, two of them are reserved for the network address and the broadcast address, respectively. Therefore, six IP addresses are usable for the subnet, which is still more than needed for a point-to-point connection and would result in wasted addresses.
A /32 subnet mask has 255.255.255.255 as its decimal representation and
11111111.11111111.11111111.11111111 as its binary representation. This means that there are no bits available for the host portion of the IP address, which allows for only one possible combination: all ones.
Therefore, only one IP address is usable for the subnet, which is not enough for a point-to-point connection and would result in an invalid configuration.
Therefore, a /30 subnet mask is the most efficient choice for a point-to-point heartbeat connection between two servers using IP addressing because it provides exactly two usable IP addresses without wasting any addresses or creating any conflicts1.

The best practice for troubleshooting is to follow a logical and systematic process that involves identifying the problem, establishing a theory of probable cause, testing the theory, establishing a plan of action, implementing the solution, verifying functionality, and documenting findings. Since the problem occurred after a change in the server's BIOS, the most likely cause is that the change was incompatible or incorrect for the OS. Therefore, the next step should be to reverse the latest change made to the server and reboot to see if that fixes the issue. References:
https://www.comptia.org/training/resources/exam-objectives/comptia-server-sk0-005-exam-objectives (Objective 4.3)

PowerShell is a scripting language and a command-line shell that is designed for Windows server administration. It can perform various tasks such as configuration, automation, and management of servers and applications. Verified References: [PowerShell], [Scripting language]

The first thing that the administrator should check is the network cable. The network cable is a physical medium that connects a server to a switch or other network device. The network cable can affect the speed and quality of the network connection, depending on its type, length, and condition. If the network cable is damaged, faulty, or incompatible, it can cause the server to connect at a lower speed than expected. Therefore, the administrator should check the network cable for any signs of wear, tear, or mismatch, and replace it if necessary.
References: CompTIA Server+ SK0-005 Certification Study Guide, Chapter 2, Lesson 2.1, Objective 2.1