Having a secondary anti-malware program alongside your primary antivirus can provide an extra layer of protection. Malwarebytes Anti-Malware Free is a popular choice and can be a good complement to ESET NOD32 Antivirus. It specializes in detecting and removing malware that may not be caught by traditional antivirus software.
Regarding performance, it is true that running multiple security programs simultaneously can potentially impact your computer's performance. However, this will depend on your system's specifications and the specific combination of software you are using. It is recommended to monitor your system's performance and adjust accordingly if you notice any significant slowdowns.
As for Norton Power Eraser, it is a standalone tool designed to detect and remove deeply embedded threats. It does not have a built-in database update feature like traditional antivirus software. Instead, it relies on downloading the latest definitions every time you run a scan. This ensures that you have the most up-to-date protection against the latest threats.
Kaspersky Free Scanner (KVRT) also requires manual downloading of the required database updates. This is common for standalone malware removal tools as they are designed to be portable and do not have real-time protection or automatic updates like full antivirus software.
In summary, having a secondary anti-malware program like Malwarebytes Anti-Malware Free alongside ESET NOD32 Antivirus can provide additional protection. However, it is important to monitor system performance and adjust accordingly. Norton Power Eraser and Kaspersky Free Scanner both require manual downloading of database updates.