Departure lines/EES?

Departure is really not that much different than previously, so I think the recommended 3 hours for international flights would be more than sufficient, doing less is up to you.

My experience with exit is that you either will use an e-gate or a manual booth. You will scan your passport, smile for the camera, then you may or may not have to scan fingerprints (my wife did, I did not), then on your way.

Is it a direct BCN-Chicago flight?

We just did a BCN->Lisbon->Dulles flight on TAP (way less than half the price of the preferred United direct BCN-IAD flight) and the EES took place during the layover in Lisbon. It was a royal mess! Luckily, there was a slight delay on the LIS->IAD flight (30min), and TAP was ushering tight layovers to a special line through EES (ie seeing a border agent), but man, it was chaotic and stressful for hundreds (thousands?) of passengers arriving during that time.

Our time through BCN security was smooth, but since we hit EES at LIS, I can't comment on the efficiency of the Spanish vs the Portuguese, but I think, with this experience and current random headaches in airports these days, I'd pad my arrival to 3 hours if 1) you can check in that early, and 2) EES is at the BCN and not a later exit connecting airport. #1 is the real limiter as security and EES will be after the check-in/bag check, so if the airline is not open yet for your flight, arriving any earlier has no value. On the flipside, I think the extra 30mins is a nice "comfort" knowing the airports seem to still be struggling with their EES implementation. Lisbon seemed to have a ton of automated EES terminals, but few - if any - were actually working properly and sending everyone to the border agents.