MacOS Mail junk versus spam

I regularly check my JUNK folder to restore legitimate emails which are often included, and then delete all the rest.

But there are also SPAM folders which are independent of the Junk filter. How can I ensure that these unread spam emails are automatically moved to the Junk folder so I don’t have to scan the rubbish twice?

If I manually move all the spam emails to Junk, will MAIL then remember that the spam emails are also junk and move them there automatically in future? Would they also retain the label SPAM which is visible in my smart mailbox for UNREAD mail?

How does MAIL distinguish between JUNK and SPAM? If the Spam emails are registered externally by Apple, then I would feel confident in just deleting them all without even checking them, something I cannot do with Junk mail.