can I remove the spacer stack and just run the stem ‘floating?
You can, but without the preload bolt holding everything down there is a tendency for stuff to walk up the steerer. That's mostly a stem problem as the off axis loads are large, but steerer flex under suspension and braking loads also shortens the effective steerer length between the bearings, which pushes the retaining clamp upwards. You may find yourself making more frequent bearing adjuistments.
You can, but without the preload bolt holding everything down there is a tendency for stuff to walk up the steerer. That's mostly a stem problem as the off axis loads are large, but steerer flex under suspension and braking loads also shortens the effective steerer length between the bearings, which pushes the retaining clamp upwards. You may find yourself making more frequent bearing adjuistments.