Which location would be better for my this type of room to install split air conditioner?
Heat loss or heat gain is how fixed heating is installed. What that means to keep a uniform temp in the room we put registers under / over windows . Where the outside temp affects the room more.
I don’t find mini splits following this quite as much possibly because there air discharge is 3-5x the area of a fixed vent and the minis usually have active vents that oscillate further turning the air in the room. By conventional setups you might want the mini over the window. Will your mini fit there it has to have room to open you have to clean the filter regularly.
Installing over a window may have you drilling the line set through a header not so easy and the lines and drain go down to the outside unit so now it needs to be off set from the window and that looks out of balance to me I would rather put it on the red wall and use the furniture and visual how it looks to mount it. So heat gain and loss with small fixed registers makes sense but with mini’s that big thing on the wall if not located in a way that it looks balanced it can negatively affect resale later.