Your RPG Builder game can be in any art style you want, using any models, textures, animations, sounds that you want, but the demo comes with samples assets only, for a full game, you will need your own art assets that you can either buy from the store or produce yourself.
Blink also produces art packs for things like textures, character models, weapons, icons, props, and so on. You can take a look at our Blink Art Store
You are the one who will design your world, inside your Unity Scenes. Any Unity scene can be used as a game scene in RPG Builder, and it is very easy to do so. Here is a tutorial that shows you how to create your Game Scenes.
You can even have procedural worlds or scenes, made with your own system or with assets such as Dungeon Architect.
RPG Builder gives you endless possibilities in how to design your game, and how your players will experience it.
RPG Builder provides you with its default Character Controller for free which is a Third-Person Action RPG Character Controller, similar to what you can see in games like Breath of the Wild, Horizon Zero Dawn, etc.
If you want a different type of controller for your game you have a few options:
Purchasing one of the officially integrated ones:
You can also use ANY controller that you want in RPG Builder, either one from the store, or your own, but you will need to integrate it yourself, to make sure everything is connected to RPG Builder. Here is the video on how to integrate your own controller, using the Controller Essentials system: https://youtu.be/Q3EjrQFJeFo