What highest security brake with wordpress and static files?

If you can’t modify anything on the server (site fully static) then there is no point in trying to break into it.

In enterprise kind of setting you can achieve this by limiting login and restricting write permission to only people coming from the local network, but for most people this kind of setting is too hard to configure and maintain, and doesn’t fit their work flow (for example you can’t post new content from anywhere in the world but only from specific location or only if using specific software).

Edit

Should have been more explicit about it, the answer is that security is a process and not application of specific tool or method. The only way to make sure that your site is secure to check that all of its components are secure and then check that they are connected with each other in a secure way.