Autoruns - Known DLL's

Does anybody know what known DLL's are? I have a bunch that are File not found. Can I disable/delete them?

Dll are dynamic link libraries. Software libraries that can be loaded at run time rather than statically included in the executable so programs can share a copy.

I believe known dll are enumerated in the registry, the purpose being to restrict their location in the windows directories for security purposes (can't be loaded from elsewhere).
So these appear to have registry entries but no corresponding dll file on the disk. Don't know why, just obsolete and not cleaned would be my guess, but I wouldn't mess with them.

Autoruns, even in administrator mode will often refuse to delete these entries - which I would always take as a "Do Not Touch" warning - If the entries are causing a specific issue, you may be able to delete them in the registry editor but backup the registry first with a way to restore them if the system fails to reboot

Should add that the SysWow64 ontains 32 bit dll while system32 contains 64 bit dll (that's correct). On a 64 bit system it is not surprising or concerning you are missing some 32 bit dll.