Do stenting procedures for carotids also clean out the existing plaque?

No, compresses it. Stenting has 2-3x the risk of surgery of stroke TIA and death. Find good surgeon with 1-2% stroke rate and don't get stenting unless you are very high risk for surgery, have hade radiation to neck or in some cases redo.
No. Carotid stent placement does not clean out existing plaque. It pushes it against the vessel wall trapping it with the stent.
No. Revascularization uses the pressure of the balloon (angioplasty) or stent to open the artery to allow unimpeded or improved blood flow. The plaque is not removed during the procedure. Aggressive medical treatment and lifestyle changes can reduce the risk of restenosis and slow plaque growth in some cases.
No. This is precisely why the recurrence rates for carotid disease after stenting are higher than for endarterectomy. The plaque is still there it has just been pushed into the wall of the artery.