My understanding is that EM is largely shift work which means you're generally not taking call, but you have a fairly heavy on-off schedule and you could very easily end up working holidays etc (which is really true for any field). There's a high burnout rate with EM compared to many other specialties. It requires a lot of energy to do, so don't think it's "easier" than another specialty just because of any hour difference. Your hours/week will also vary based on your career trajectory and practice environment.
EM is on the low side of things, but again, don't assume that means it's easier or that you're guaranteed to be below a certain # of hours/week.
Get into med school first, then talk to some EM attendings and advisors and see what they say.