In the Charlotte region, there is a tradition of showcasing some of the largest and most impressive homes on the main thoroughfares. If there is a difference between property values for Farmwood homes on Matthews Mint Hill and the interior of the neighborhood, it almost certainly is already reflected in the price. You should be fairly confident that there is not going to be a future decline in value based on the road. And if more of this property or additional easement is needed for a widening, you could expect to be compensated by the state/county.
The water situation is something you would need to investigate for this specific property. If it is on Matthews Mint Hill Rd, it is most likely to have county water, but it might also be on a well. The cost would of course vary with the source. If on county water, you should expect rates to be equivalent with other areas of the county. Details can be obtained through the CMUD website http://charmeck.org/city/charlotte/Utilities/Pages/Home.aspx or phone lines.
But there are a lot more factors to consider than traffic, property values and water when purchasing a home...If you have a full time agent with a Masters degree in Planning with Finance and over two decades of experience, working for you, you will likely do better in negotiations. I'd be pleased to provide that service. ...and if you like this reply, please give it a "thumbs up" or "best answer".