You're mixing a few concepts. uTP was designed for minimizing congestion, while still maximizing throughput. It does add some overhead, which we'll work to reduce. The effective rate of throughput minus overhead (sometimes called "goodput") is slightly reduced as a result, but this is a small price to pay for a more responsive network. We're working on lowering the overhead, but outside of rafi's scary-looking graphs, you shouldn't have any serious problems with it.