As
@FireBorn pointed it out so well, angels are higher frequency beings, while demons are usually lower, although even among them, you see surprisingly high vibrational ones, and same goes for angels; there are some fairly low vibrational ones you may straight up accuse to be 'demonic', following the same logic.
Appearance wise, well let's just say, energetic beings does not have a physical body, so they can take shape any way they like. The aesthetic they chose usually delivers the energetic structure of their essence in a visual way, in which you get what you meant to see, or wish, or
they wish
you to see. Visualisation is important, and it's easy to discover 'preferences' in how they usually show themselves (individually); although, it can still vary based on the conjurer.
Why are they mentioned as different entities? Because they
are different entities.
Every 'group' of entities has their frequency, general nature, so called 'culture', habits, their kind of 'moral' and just like in every sentinent being's case, they all have personalities of many kind, which means some can go against what you'd expect them collectively.
I've seen angels one would wholeheartedly call a 'prick', or straight up
dangerous, and they are not necessarily less fond of bonding in a more sensual way demons are often described to. Yes, I had angels come to me for astral sex too. The line is blurred, and if you dive deep enough, deeper than the surface, you'll realise that angels are, in the common sense, not necessarily the
'good guys' people used to describe, typically.
And it's totally fine, because they
don't have to be.
Same goes for demons. They don't have to be 'useful dicks', they can simply be 'useful'.
Matter of fact, my demons were quite caring and dedicated to me, and some highly protective without being asked.
Many times they proved to have greater patience than most angels do. One of my friend literally pissed
Archangel Michael off, and knowing her, I totally seen it coming. I have a close and old bond with Michael, so I am not caught off-guard by it, and I share the same with Lucifer himself.
They work quite well together, without an issue by the way. So, while I've seen my friend just making Michael 'quitting' their work (she's with Beelzebub now, and doing better than ever), I have Paimon in the other hand, who you'd expect to be very demanding, yet he was totally fine with me ghosting him for six years, until I finally settled. He always sent me signs here and there, but never lost cool, never went furious, never grow violent, and he is very eager we finally get to work together.
An another thing I noticed, is that demons are more of a '
yappers', unlike angels. They prefer to stay behind and communicate in less 'straightforward ways', while demons
(exceptions exist, naturally) are generally love stepping out and work directly. They also rarely refuse a task, or a request. Angels are more 'picky' about what they're willing to help you with.
Usually, it's for your own sake, but let's be real, allowing you to do stupid things and learn from it is also a good way of teaching coming from demons; I'm with them on that one. It's not their fault if someone want to cause an issue for themselves, as long as they pay for it.