I take somewhere between 2-4 minutes at the car. My bag stays attached to its pushcart, but I make sure everything is in it, and set my phone, smokes (I know, they are bad), keys, etc. into their respective places in the bag. It takes me longer with a cart because I load the balls/tees in, and have to switch the slot of my driver and 4W to make them accessible. I want the head of the idiot that designed golf carts that have the roof of the cart overhanging the bag area.
Playing wise, I am the fastest I know by 25%. This is a very conservative estimate. The way I see it, the faster I play, the more chance of a second round on a weekend. For some people its a leisure activity, but I get my excitement from hitting the ball, and if I can see twice as many holes on a given day, then I will attempt to do so.