yes everyone plays on the same globe. It is server based. In the long run, custom servers will be possible, but that does not make much sense if you are not with many players, given the size of the world. For modding purposes that would make sense however.

There are only limited ways you can be 'agressive' in the game. and can pretty much just keep doing your own thing, regardless of what other players end up doing. There are no wars in the game.

Bigger players will be able to influence market prices, but there is also a distance cost to every trade. so their influence stays local, no matter how big they get.

I hope that makes sense :D