We have a 6x8 coop, so very similar to you. We have more than 4 chickens, so we did a ladder roost. Partly so the chickens could easily get up to the highest roost, and down without injury. We do have 2 full size Black Jersey Giants (the male makes a *thud* when he jumps down off the lowest roost, so it was a good choice to do it this way for our flock. to Maximize space, we placed the door to the side, and put the nest box (2 boxes) to the side of the people door. We put the chicken door as an integral part of the people door. Here are some pics, but some are from prior to getting everything done.
View attachment 1614356
View attachment 1614357
Here are the Jersey Giants (1 male, 1 female) on lower roost. They were only about 4 months old in this picture! They are even bigger now. The coop is elevated about 2.5 feet above the ground and the male (named Jupiter) has to duck to get under the side support beam.
View attachment 1614358
Good Luck!