There’s no size limit apart from the memory space needed to store your world. With procedural generation, Godot (like any other game engine) is able to create endless worlds.
The only limit is the user’s memory and how detailed everything will be. There is also the Von Neumann Bottleneck problem where data processing can’t keep up because of the Computer’s architecture. The only way to solve this is to make a computer that does not use the Von Neumann architecture however this would require many years of development and could have more problems then the meta right now.
Is this maybe a reason for vehicle lagging? I made a spaceship game (3D) and whenever i fly too far from the origin-point the 3d model starts to lag or better vibrating. Its a little annoying.