Just wondering how many people in the world are holding or trading BTC
For that question there is now way to give an accurate answer.
You as a person can own several wallets with several adresses inside.
This means that not one adress is one person.
Bitcoin days being destroyed might help here, but I'm not really sure about that to be honest.
What we can say is that there a lot of coins hold in cold storage! And around 2-3 million coins seemed to be lost forever.
So what you see on the exchanges on coins getting traded back and forth is really a very small number, just a few hundred thousand coins, that's it.
So most of the coins are not in circulation and are in hands of really strong HODLERS!