What is the best way to throttle download speed other than setting a maximum?

What I would like to do is to have steam take lower priority over other applications requesting transfer rates. Instead of limiting the bandwidth, I would enjoy having the ability to maximize it depending on other consumption coming either from my PC (YouTube, Twitch, etc.), or from someone else's (other games, also streaming and watching videos).

If it is currently possible to do this then I haven't found how and would appreciate being shown!