See the answer below in explanation part.
Explanation
Answer of both steps below.
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The technician should check the MAC filtering list next as the new router may have a different MAC address than the old router. References: CompTIA A+ Certification Exam Guide, Exam 220-1001, Page 332

Explanation
To enable network printing, the firewall needs to open the ports that are used by the network printers and the print servers. Two common ports for network printing are 515 (LDP) and 631 (IPP). LDP stands for Line Printer Daemon Protocol, which is a TCP-based protocol for sending print jobs to a remote printer. IPP stands for Internet Printing Protocol, which is a HTTP-based protocol for managing and monitoring print jobs over the Internet. According to the CompTIA Core1 objectives, one of the network ports that is related to printing is
515. A research paper on network printing also mentions that LDP and IPP are widely used protocols for network printing.

The message "The amount of system memory has changed" indicates that there is a problem with the random access memory (RAM) modules in the computer. The RAM may be loose, faulty, or incompatible with the motherboard or other components. The GPU, HDD, and CPU are not directly related to system memory and would not cause this message to appear.

The best option that the technician should do to optimize performance is D. Utilize all channels. This option means that the technician should install the RAM modules in a way that maximizes the number of memory channels that are used by the motherboard. Memory channels are pathways that connect the memory controller to the RAM modules, and they allow data to be transferred between them. The more memory channels that are used, the higher the memory bandwidth and performance1.
DDR5 memory supports up to eight memory channels per module, which is twice as many as DDR42. However, not all motherboards can support eight channels per module, and some may only support four or two channels per module. Therefore, the technician should check the motherboard specifications and manual to determine how many memory channels it supports and how to install the RAM modules accordingly.
For example, if the motherboard supports four channels per module, then the technician should install four RAM modules in slots 1, 3, 5, and 7 to use all 16 available channels. If the motherboard supports two channels per module, then the technician should install eight RAM modules in all slots to use all 16 available channels. If the technician installs fewer modules than the number of slots, then some channels will be left unused and the performance will be lower1.