The house is a 1950's house, that has been extended more recently, about 2005. The bedroom I am using is spans both sections of the house, so the construction and dimensions change a little bit - 2/3 of the room is the 1950s materials and dimensions, then another 1/3rd is the modern equivalent.
I have attached a diagram that hopefully shows what I mean. The part that has me stumped is how the dimensions of the room shift slightly, creating these "shelves" in the walls, ceiling and floor. I am not sure what affect, if any, this is going to have on the acoustics and what I should do, if anything to mitigate...
my goals are simply to tame the room response a little bit, its quite a "peaky" room especially with the low end (no surprises there). because its quite thin (~2m) with a door at one end and an L shaped desk I dont really have a lot of leeway to play with the position of the monitors much. In the top down view, the monitors are the small squares and the circle is where i sit at the desk. I have indicated the monitors sitting on their stands on the side view as the rectangular object.
Obviously there is a lot involved with room treatment and I am busily researching all of that, and dont expect anyone to do all the work for me. I just specifically want to understand how the unusual shape of my room might play out, compared to a symmetrical one. For example, I am considering the are where myself and the monitors are, and how its slightly wider than the other part of the room creating a little vertical shelf in the wall to my right. Some of the things im thinking are, should i place the monitors based on the wider part of the room? this is the current setup, but if you walk into the other section of the room then the monitors are now uneven in the context of that room section... it seems like that shelf of wall is going to reflect things anyway regardless, can i just "wrap" a panel around that shelf to mitigate that... or would it be better to try and "fill in that gap" so the room has a more even width? It seem like it might be a good idea to use that space to create some sort of bass trap, but will having one large trap on the right and relatively nothing on the left be an issue, perhaps more of an issue than just treating it like a normal room..?

I suppose that I am at a point where I am ready to start building and testing stuff out, but I would really like to know if these strange little steps in the room dimensions should be something I base the whole treatment around, or on the other hand they might have no great effect and I can just sort of ignore them? I really have tried to google this but I have not been able to find any examples of a room like mine.
I realise I am pretty short on details in a sense, but I am kind of stuck on step one which is deciding on those details/how to proceed based on the actual room shape. Hopefully my question is clear and specific enough to be answered easily, if you think theres more details that would be useful let me know. Thanks -Nik