Our set up (not including fast track) is 1:4 for emergent and 1:3 for urgent. Urgent gets the brunt of hallway pts so the initial ratio is lower but will double when we're rocking.
We practice prn team nursing. Everyone takes care of their own pts but if you get a code, critical care 1:1 or squad and triage arrive simultaneously, then you'll get assistance as needed. If you're 1:1, your pts get split among everyone else or taken by the float (if one scheduled). For codes, charge and anyone free comes in and there's always at least one rn who's caught up. For simupatients, generally someone will offer to start one if 'em which in our er includes line/lab.