If a hacker succeeds in using my Apple ID to log his device into my iCloud account, can he spy on my devices well enough to hack into my web accounts?

I ask, assuming the currently latest versions of iOS and MacOS.

Can he capture keystrokes created on my devices? Can he access my Google, Yahoo, etc website accounts if I'm logged into those sites, assuming he finds ways to overcome my two-factor authentication methods?

Can the Terminal app on one device execute commands to spy on another device, or even modify its software?

In particular, I wonder how Continuity features could be exploited.

Thank you for any insights!