Hi @yavin 

Thanks for posting in our business forum.

1. This is a fanless switch. It's normal to feel warm on it as it's passive heat dissipation.

2. Do you have any SFP module plugged into this switch while the fiber/RJ45 is not connected? If you do, then it's normal. It's the CPU design.

3. First we need to know the fact that there is a difference in CPU usage between the router and the switch. The router is relying on the CPU performance to forward the traffic according to the routing table while the switch is using the MAC chipset(AKA ASIC chipset) to process the switching. CPU usage does not affect the performance of the switch.
CPU usage relates to the maintenance of the Routing Table, ARP table, IGMP Snooping, STP and Loopback Detection, etc. The more advanced functions you enabled, the more CPU the switch uses. Regardless your network load, as long as they have been enabled, it takes CPU usage.
Core switches generally have higher CPU usage than access and distribution layer switches because they perform more complex functions and handle a higher volume of network traffic. Core switches are typically responsible for forwarding traffic between multiple network segments, which requires more processing power to ensure efficient and reliable network operations. Additionally, core switches are often responsible for routing protocols, security measures, and network management functions, which also contribute to higher CPU usage. In contrast, access and distribution layer switches focus primarily on providing access to end-users and connecting to other network segments, and typically have fewer processing requirements.