Godot has a tilemap and tileset editors in the editor. But you can also set tiles or delete them programmatically for an in-game editor. That is fairly easy.
However, some of the asset importing tools only run in the Godot editor. So it would be easy to allow users to remix the art you make, but it becomes complicated if you want to allow them to upload their own art or mods.
I've seen people do it, but it requires add-ons to the engine. Definitely possible, but not built-in.
There is some vector support, but it gets rasterized when you use the asset (for example, you can import a svg file, but then it becomes a pixel sprite). You can create curves and lines with code, but it depends what you are doing if this is worth it.
There are a bunch of tutorials for 2D games, this one is my favorite: https://www.gdquest.com/tutorial/godot/
I'd stick with Godot 3.x, as 4.0 is not finished and only really beneficial for higher end 3D.