We've had several setups.
When my twins were really tiny, they slept on one side of my kingsize bed, with a mesh toddler rail along the side. I then had the other side of the bed, with a single duvet. DH in another room.
When they got to be too big to sleep side-by-side one one side of the bed, I let them have the full width and I slept across the bottom! Toddler rail down one side, cot on the other to stop them rolling out.
Having seen me across the bottom of the bed, my DH shuffled everything around for me while I was away with the babies. We now have the kingsize bed against a wall, with a single bed next to it. They have the kingsize, I have the single.
In all cases, I feed lying down on my side, moving to lie next to each baby with the correct boob lowest. I stick to one twin, one boob through the night so that neither side pops.
I put them to bed in the big bed at 7 ish. Neither of them can roll back to front yet, and I gamble that they're unlikely to master this at night, in sleeping bags, and manage enough rolls to get off the kingsize and across the single to fall on the floor. I also put the kingsize duvet over the ends of their sleeping bags (up to about their thigh level) to make it harder for them to roll (and so duvet is there for me when I'm feeding. I then get in the single bed when I go up, then shuffle between kingsize/single as and when I am feeding/wake up to move back.
I guess I don't have long before they'll be mobile enough to fall off the side/bottom of the bed. My plan would be to move the beds out and put the mattresses on the floor, but I suspect the more sensible plan would be to move them into cots (either in my room or their own). I will be so sad to end these cosleeping days though. Nothing beats waking up with two smiley babies in your bed!