Hey there @Agonaute13! Welcome to the community! Skyrim-like is a tall order for one of your first games, even only making a small slice will be tough, so be ready for a perilous journey!
The short answer is yes, Unreal can handle both instances and full open worlds, though the latter is harder to manage. It all comes down to your needs and the scale of what you’re trying to accomplish. World partition was designed to handle chunk like loading for open world games, but gets a bit harder to manage at supermassive scales. Level streaming was built with instances in mind, where you’d stream in pieces of the levels you want when you need them, and larger level differences would be separated into their own instances altogether.
Side note, depending on the day and who’s on when the question is posted, it’s sometimes easy for some to fall into the cracks!