Mining with a GPU will use exactly the same bandwidth as with ASIC - on a comparable DGB mining payout basis that is
Let's put numbers. We're talking at about
hundred bytes per minute.
Right, you can't mine and play at the same time, but you can mine when you're not playing, and get some nice amounts of DGB doing it.
You can absolutely mine and play at the same time, just not with AAA games. In practice many games games are mostly bandwidth hogs so GPUs have plenty of spare time. The highest-profile games I played while mining were Borderlands 2 and some HD remix of Serious Sam. I've mined Qubit, GrsMyr, even NeoScrypt. Qubit works like a charm, little impact on both framerate and hashrate. As a comparison, Yescrypt is incompatible with everything. Best part is power consumption since your GPU is already 90% loaded when gaming so you get only part of the hashrate but at a fraction of the cost!