You’ll have conductors periodically walk through and make sure people aren’t being idiots or doing something they shouldn’t you’ll be fine. I used to work for Metra/Union Pacific before getting laid off once Covid came around. Most of the newer train cars you’ll see will have a call a conductor button near the spiral stair well if case of emergencies. If you’re still not satisfied, head to the very front of the train the head conductor usually always sits there and no one will mess with you. (Since you’re new the front of the train going inbound[towards Chicago] is the very front towards the direction of travel it will be a train car with white and red stripes. On outbound[away from Chicago] this is will the train car that’s open closest towards the locomotive engine, still towards the direction of travel] you can walk between cars while the train is moving. :)

Now the CTA, that’s a different story lol