I would say it runs before the Justice-Doom War but it definitely takes place during Snyder's run. Clark's identity reveal, Alfred's death, and John's ring point to it being some point post-6th Dimension, although there is no doom in the sky so maybe those events (Alfred and Clark) happened earlier than they were revealed, but the ring definitely means post Totality arc.
I'd say so, all you need to know are thing you'd see in headlines; John's a human power ring, Alfred's dead, Clark is outed as Superman, everything else seems pretty self-contained