Angel or Demon

I have 4 Angelfish in my 180litre community tank (they have been together for 8-10 months now) and I have noticed more recently that they are or may be juggling to see who is or will be boss. Or are they just playing?

In the photo the one with least amount of orange is the one that seems to be at the centre of all current actions (we call her/him Cruella). The one at the bottom of the picture we call Sonny. Cher is pictured at the top and Prayer is pictured in the middle. I have no idea if they are male female or a mix of both.....

Now Cruella and Sonny are the ones that seem to start things and quite often head butt each other as if telling each other to get out of the way. However Cruella will also annoy or chase Cher and Prayer too, they will also react to the action and none of them ever really wish to back down.

There are no damages caused to any of fish so I am thinking it is more playful rather than fighting..... but of course I wish to ensure it remains that way the last thing I want or need is them to start taking chunks out of each other. If it is more serious than playing I will of course need to take actions. At the moment they seem to know just how far to push things without causing damage, but I am a little worried that it could escalate to another level and at what stage I need to intervene?

How concerned should I be?

Angels get nasty when it comes time to grow up. They can be the best of friends til then.
Demons?
Nah, you need Satanoperca daemon eartheaters for that role!

I would be quite concerned. I love keeping angels, but when it comes time for them to sort things out, they don't love each other.

And it gets even worse if two of them form a pair and decide to start breeding. Then you'll almost certainly find the other angels huddled against a side of the tank because the pair have taken over and won't tolerate the others in their territory anymore.
I would love to keep angels one day. But it seem cruel to me to keep one alone, and very difficult to manage a group successfully, and beyond my current abilities...

@Colin_T knows a lot about this group dynamic issue with angels though, hopefully he can help you out with sexing/what you need to do!

"Angelfish" = misnomer...lol

So far, from your description, they are behaving normally for the species. This is what one expects. The risk is what may occur down the road.

If you have male/female among the four, a pair may form, and then you may soon have a pair and two dead fish. The 180 liter tank is no where near sufficient size for the roles to play out safely, always assuming your fish are healthy and "normal." It is their inherent behaviour. In the habitat, this never (or rarely) causes harm because if a pair from within the shoal form, they do their thing and the other fish move away out of harm's way. This is not possible in an aquarium except in a truly large one.

Pushing and shoving is certainly normal behaviour. Lip locking usually is getting more serious.

Thanks guys I will keep close eyes on them for now then.
Another question........ is there anything in their behaviour which would help sex them? Like some sort of tell that would make me think ah you are male and you have to be female? I'm guessing the answer is no.......
The only real thing for sure that I can see that is consistent in their behaviour is that it seems to be Cruella that is the main trouble maker (or at least that's how it looks).

The breeding tubes are the best indicator of gender. Females are thicker, males are slimmer (the breeding tubes I mean). I cannot see these in the photos. Some mention head shape but others say this is not reliable at all.