Can a charcoal grill maintain a constant high temperature? In the example in this question I mention getting the grill to 400 Fahrenheit. This example is not in a vacuum. I really do need to roast my brussels sprouts at 400 Fahrenheit and I won't necessarily have oven space as it is Thanksgiving. So my question has evolved. Most charcoal grill recipes I have read involve temperatures in the 200 to 300 Fahrenheit range. Can I get a charcoal grill (for this example consider a Weber kettle grill) to 400 Fahrenheit and keep it there consistently? 

Also, if I add smoking wood, will that change a lot? I am glazing brussels sprout in black pepper, bacon, and maple syrup if it matters and I will smoke them with whatever is available at the house. The recipe I am using involves roasting them in a pan, so I would prefer to keep it that way (lest I have to clean the grill).
The recipes you are referring to are probably for BBQ/smoking, rather than grilling, which happens at a much higher temperature.  It is fairly easy to get a kettle-type grill to reach 400 F (and well beyond).  The challenge will be maintaining your desired temperature.  However, that is what the vents are for.  There should be a vent on top and a vent on bottom.  With a little practice, you should be able to manipulate the vents to maintain the temperature.  Try to overshoot your mark by 25 - 50 degrees F before you reduce the airflow. You will get some smoke flavor from the charcoal, particularly if you use hardwood. The addition of smoking wood will add stronger smoke.  For vegetables, I would stick with fruit woods.