What kind of process have to go through? Who make the final votes? I guess the change is similar to implementing BIP.

I heard many posts here said "Economic Majority" vote decides. Does this mean who hold the most bitcoins decide? Maybe not. I guess BIP is determined by Bitcoin Core developers, so the total bitcoin supply (21 million) is also determined by Bitcoin Core developers.

Also, the argument against the "Economic Majority" is it is often the case we can't find holder for the addresses with a lot of bitcoins. How can we contact them for vote?

Thank you indeed!