Hi,
If you install Windows Security update package, it will strengthen security protection for your computer, it also will addresses other issue which might expose computers to a security vulnerability.
If you install monthly Rollup which include both security and reliability updates that are packaged together, addresses both new security issues and nonsecurity issues occur in system, to make system run stable and security.
If there is something wrong with your existing system, update system is helpful to troubleshoot system issue, and will address some issue with the latest update package. If you perform upgrade, such as to latest Windows 10 20H2 or 2004 version, it similar with a system repair with load system files again through upgrade, it will address most of system issue caused by misconfiguration or system file corruption.
Windows update in Windows 10 is different with Windows 7, we can't disable update permanently, I would recommend to update system regularly. If you encounter system issue, please try update or upgrade. You also could reply to us with your detail information about issue to troubleshoot it.
If my information is useful for you, please kindly mark it as answer.
Bests,
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