I have found a nice collection of detailed architectural drawings so making a good model should not be a problem.
However the height values are confusing me. The castle is situated in a lake with gardens, courtyards etc. placed a few metres above the water.
What would be the correct reference point? If I use the water level as a reference point for the height values the walls on the inside will be too tall but if I use the courtyard as reference the walls facing the lake will be too short.
The best solution would be if the courtyards could somehow be rendered a few metres above the water level. Is that even possible without tagging them as buildings?
In your case the lowest ground level looks to be the same as water level. There is grassy shore coming down to water while also touching the wall. So water level seems to be the reference height. Except it’s going to change every time the moat seasonally dries down and fills up