You need a black & white striped shirt befitting the referee you have to become!
Sooner or later, one or both of these kids is going to leave home for a college room 2/3 the size of the room they have now, or an apartment with either a roommate in the same bedroom or a tiny place with paper-thin walls. So the time to learn cooperation skills is now.
It may be that they are still adjusting to the new family arrangement (with shared custody) and new house, or that they are entering the dreaded Hormone Years, or both.
I don't think there's as much risk to an earbud wire wrapping around the neck, but I do think it's a recipe for damaged earbuds which they will want you to pay to replace. And there are some concerns by many pediatricians about iPads and iPhones too near the head during the long period of sleep, so even if they are using those for alarms, the electronics need to be a few feet away. I think they both can get ready for bed earlier than "lights out" to minimize the disturbance to the other, or one can keep his pajamas in the bathroom and change there when he is doing his teeth and taking a shower or whatever he does before bed. I think a sleep blindfold is okay for the early-to-bed kid.
I think they are perfectly capable of working out a compromise schedule, with the threat (oooops, I mean "promise") from you that they have one week to set it up or you will take away the electronics and book lights, and dictate an earlier bedtime for the night owl and no play list for the younger one. They can learn to sleep like all of us did in ancient times, with the lights off and in the quiet. Anyone who complains that he's "not tired" can come downstairs and help pick up the house and walk the dog instead of you always doing it. I think it's fine, now and then, if a kid crawls in bed with a parent, but down the road, this isn't solving the problem. And while you're not thinking this way right now, you may be in a relationship at some point and/or you will want your own privacy just because you're beat and you're the mom.
You could consider one of those folding screens to separate the beds and block the light - you can often find one at a discount store, and the two can cooperate to paint it if they want to.
Good luck. If it gets ugly, call me and you can move into my guest room for a few weeks while they fight it out!