If I'm playing somewhere that doesn't have backline, or only has a weedy PA, I have three racks that get trotted out:
A 2U rack for my Eden WTP600 head.
A 4U rack that holds my stand-alone IEM set-up.
A 6U rack that holds the PA amps and crossover.
One thing that really speeds up setting up and packing down is panel-mounted connectors on the back of the rack. The PA rack has four Speakon connectors and two XLR connectors for the mixer, with the electric string tied neatly out of the way inside the rack. Everything's labelled and colour-coded, so the only thing to ensure is that the colours on the cables match those on the connectors. The IEM rack has labelled XLR and jack inputs and outputs, with the IEM transmitter permanently connected to the rack mixer via a jack cable with right-angled plugs front and back.
The only fiddly bit is the backline speaker connections. The amp has a cycle switch that changes the colour of the Speakon sockets between 4 ohms, 8 ohms and 'do not use'. I've not yet found a reliable way to extend that to a rear rack panel, so there's a bit of faff involved in plugging the cabs into the right sockets.
But apart from that, I've found that carefully-designed and wired racks can save a lot of time, especially at the end of the evening when I just want to get out and get home.