Well mine at 580+rwhp is still very street friendly. Can't speak for the over 600rwhp level.
With the mods in my signature I usually run a stack setting that is around 425-450rwhp. This setting is responsive, smoke is not a problem and mileage is as good as it has ever been with normal/conservative driving.
The better matched combinations with proper installation and all supporting mods in place will be street/towing friendly to some fairly high hp/torque levels from what I have seen.
And as stated above I can always turn down boxes or downloaders for towing or other conditions if necessary.