HQ tree count is the amount of trees that will be rendered in 3D (not necessarily HQ, only trees close are HQ) in a radius around the golfer. Having it set higher than the amount on course shouldn't affect performance. Setting it at 2000 trees is enough to render all the trees in 3D on most courses, but may need to lower that if you don't have a high end system.
The distance setting? The distance setting limits the 3D radius around the golfer no matter what the tree count. So I leave it on max and set the tree count to 2000 or less if needed for better performance.
Those figures are for a detail setting of 1, which is all you really need. For detail setting of 2 since it renders double (which does help with follow cam for distant objects from popping into HQ) you can drop the tree count down to 1000 for the same coverage. Going above detail 2 is a waste of resources as you can't see any improvement in visuals. Those HQ bushes 1000 yards away won't look any better from your golfers view.
