You start with the bed what size does he want. As for style that is IMO up to him this is his space not yours really. This is not a big room so every thing chosen needs real thought He needs a closet so now the space is 11 ' 10" x 11'8" since the closet needs to be 2' deep and add doors .IMO the closet to the left of the door makes the most sense .I do need to now where both those doors go to. If a single bed is okay with him then he has a bit of space to play with for gaming . I would put the bed against that wall next to the top door if it will fit without overhanging the window Does the windo go to the floor? Can you maybe post a pic of the space . With the layout I mention he could do a gaming cahir in front of the window and have the right wall done with the desk and whatever he needs for gaming.

He is almost an adult, ready for a job or college. At this point you need to be helping him develop his decorating skills and logical thinking. Start by having him list the must-haves in his room. Show him how to use graph paper so he has a realistic idea of what will fit in his space. Guide him in color and pattern selections. He needs to set a realist budget ( as I told our kids, “ everyone has a budget: some are higher than ours, some are lower, but everyone has a budget.”). There are many life lessons to be learned here. Jump on this opportunity to teach him.

Why does the BR have 2 doors? Can a dresser or wardrobe block one door to help with furniture layout? Room is barely big enough for a queen bed so if not practical, ask him if he wants a twin XL bed like a college dorm or a futon/ sofa bed that he can sit on for gaming or reading? Ask if he does gaming on a tv and needs a tv stand (or wall mount tv) or a computer that needs a desk. Ask if he prefers a chair specifically for gaming. Ask him if he uses a desktop PC for school or if he uses a laptop (Ask if he prefers to use laptop sitting on the bed, at the dining table, at a desk in his BR.) Ask if he prefers to hang up his clothes and needs a wardrobe unit or if he prefers a tall dresser, or takes advantage of floor, lol. Does he read in bed and needs a bedside lamp?

You need to add the WHERE of the doors, the size of the window. Show a picture of the existing space. As is.......

I can create a layout, I think we all can but I will need measurements of the room, wall heights etc

The style mixture is easy enough to do but you want it to have some of your son's touches as well. I see you're using RP, I have that on my laptop as well. Show a wide view picture of the actual room.

Good advice in all those comments now we need info from you. Please post pics here in this post do not start another

As Patricia Colwell said - start with the bed (since this is a bedroom). Determine the size your son will need. That will dictate most of the rest of what you can do with the room. Good luck!