I really want to get this game now; but for some reason there's no crossover between Steam and GoG. Which really sucks because I would much prefer to move over to GoG but most of my friends play on Steam.

So that begs the question, how many GoG users are playing NMS right now?

No one will be able to answer this, unless I missed GoG publishing any numbers on online players. In my limited experience, I've mostly seen the same players pop in when I played Online.

Also, I do not know how NMS distributes load. E.g. if you try and join a random game, it might try and have you join the game of a player within a certain region or latency limit first -- which then naturally leads to people more or less seeing the same faces all over again and again.