Blender 4.2 and newer. It is tested on Blender 4.2, 4.5 and 5.2 LTS.

Yes. Choose the curve plan and draw a curve (closed for a circuit, open for a wall run); the walls, towers and gate follow it live. Set Ground to Your Terrain to stand the castle on any terrain mesh.

Yes. The castle is real-size meshes with UVs and Principled BSDF materials using image textures, split into named parts (walls, towers, gatehouse, keep, buildings, wood, flags, ground, water). Convert to Meshes keeps them as plain objects ready to export, and the Low detail level keeps the polygon count down.

No. While you drag a slider the castle rebuilds in a fraction of a second; furniture and siege engines follow a moment later. Interiors, furniture and engines can each be switched off, and the Low detail level keeps polygon counts down.

Yes. Windows, arrow loops and doors are real openings through the walls, the floors and stairs are walkable, and the rooms are furnished with fires, torches and candles that light the interior in Cycles and EEVEE.

They are CC0 textures from Poly Haven, bundled with the addon, so the materials work offline and you may use them in any project.