Strong
You can move things in your head. The object turns, the route unrolls, the furniture goes back against the other wall and you can already see whether the door still opens — and none of this requires the thing to be rendered in detail first, which is why this channel runs independently of the picture. It works on abstractions as readily as on objects: the structure of an argument, the dependencies in a system and the shape of a schedule are all things you can pick up and rotate. The characteristic experience is arriving at a structural answer before you can explain how, because the checking happened somewhere without words.
Moderate
You can do some of it, with effort and not for long. Simple rotations and short routes are available; a complicated rearrangement tends to slip before you have finished checking it, and at that point paper is faster than persistence. This is a workable middle and it has a real advantage over the top of the scale — you tend to externalise early, and a diagram on a page is available to everyone else in the room, whereas one held internally is available only to you. The cost shows up under time pressure, when there is no page and the answer is wanted now.
Faint
Mental rearrangement is not a tool you have. Asked whether the sofa fits through the door, you measure or you try it; asked to imagine the route from the other direction, you retrace it rather than flip it. This says nothing about spatial competence in the world — people who report almost no mental manipulation navigate, park and pack perfectly well, because those tasks let you look while you act. What it does mean is that structural problems get solved outside your head: on paper, in a model, or by talking through the pieces one at a time until the arrangement holds still.