Is an complete open world game like http://wurmonline.com/ possible in Unreal Engine?
Did not played Wurm, but games like Player Unknowns Battlegrounds, ARK (full list of games https://en.wikipedia.org/wiki/List_of_Unreal_Engine_games ), and many others show that you can very well build an open world based game. When it comes to a server solution you could use for instance gamesparks.com or setup your own solution for storing, loading, logging players. However, with such a project performance optimizations are important, meaning how you setup your world, levels, loading etc. There is a steep learning curve until you understand all the different aspects which require attention, starting with preparing assets, how to setup landscapes, how to stream or load levels etc.
So if this is your first game project, i would recommend to start with a singleplayer prototype. Content can later be used in the main game.
Thanks for the quick reply, all the games you listed (that i know of) did not have custom terrain editing like wurm, and thats the main reason i’m not sure if it would work with unreal.
For general terrain editing see also