The opening width approximately is about 90" from Wall to Wall. It is vented in the back with a round duct to the outside. They are front loading washer and dryer, Samsung and whirlpool make them. they are about 27 inches wide each but you need to allow enough room for the hinges and a few inches on top of that to get them in, the depth Has to be super deep like about 36 inches if I remember correctly to allow room for the duct,
The plumbing has to come out in the correct location so it needs to be thought out with your
Designer and or your contractor. Please confirm all of this with the manufacturer specs
Prior to doing this. You can purchase the units at any pacific sales or appliance store close to you.