There's so many things to describe, different levels that you'll see depending on how close your relationship is, and as you say some things are too hard to put into words and are more just vibes, but I'll go through some that come to mind now. Obviously this isn't scientific but I know/ have known well in the last 4 or so years at least 3 very narcissistic people and these are more or less traits they all share. There's different types of narcissists too, the main difference I've noticed is that they basically act the same but some want pity and others want to be feared/respected.

The main things:

• They want control of every situation and person
• If they see someone who is empathetic they will seek to latch onto them and use them. If they are jealous of someone they will seek to bring them down.
• Are incredibly judgemental while also being unbelievably fragile.
• Often diagnosed with BPD or bipolar or something similar, I can't speak for all cases but it does seem like it can be because they are not honest about their behaviours to their practitioners. I knew someone who didn't respond well to any medication or treatment for bipolar who was clearly a grandiose narcissist. Obviously this doesn't mean they didn't also have bipolar but if they did the medication probably didn't help because narcissism compounded their problems.
• Huge victim complex

On a casual level (ie things you might observe if they're in your circle, rather than a close personal relationship):

• Bringing conversations to themselves, or if that doesn't work forcing themselves to be the centre of attention by talking over or loudly acting out. If that doesn't work starting a separate conversation or a new one that they can control.
• When they tell you about themselves, things that have happened to them, past relationships friendships etc: according to them they've never been in the wrong (at least not in a major way). Everything bad seems to happen to them. They are so hard done by and are completely undeserving of any of it.
• They probably "hate drama(tic people)" yet always seem to be at the centre of it.
• Often have high aspirations and berate the aspirations of others.

On a closer level:

• They don't care about you and your achievements, this comes in many flavours. The ones I've observed are: pretending to listen and care but never being able to bring something you've told them up; saying the bare minimum and bringing the conversation back to themselves; outright putting you down over it as though it's not worth mentioning or even bad.
• Almost entirely incapable of honest self-reflection, empathy, genuine apologies, or self-improvement. Even on a subreddit for narcissists who acknowledge they have it like /r/narcissism you can see despite understanding that they will never be truly happy this way and cause pain to everyone around them, many would still rather chase the high of feeling superior in their own world.
• Will screw you over in some way and guilt trip you into feeling bad for them somehow.
• The biggest way they exercise control that I've seen is through social circles. You can bet every time something happens they will tell everyone they know their distorted version with themselves as the hero and whoever "wronged" them as the villain. This was the most consistent thing across narcissists I've known, though the size of the social circles were different each time.