Which aircon set up will be more efficient?

I'm moving into a 50 year heavily remodeled room in the third floor of an SRC building. The entire area of the unit is about 45 square meters.

However I only need to cool a space of about 15畳. The first 14.7 square meters are an LDK which is connected to a 和室 on one end and a halfway that leads to the rest of the apartment on the other end. I plan to block off the space from the LDK to the hallway with an insulated curtain as there is no door.

The layout of the apartment means an aircon placed in the LDK would face directly towards the 和室 doorway.

There are no doors between the 和室 and the LDK either. However there is another curtain rod which I can use.

My options are:
1. put a 14畳 aircon in the LDK
2. put heavy curtains up in the doorway between the LDK and 和室, then put a window AC in the 和室 and a 10畳 normal aircon in the LDK.

Both options have roughly the same initial cost, but I'm not sure about the long term cost. I like option 2 because I like to be cold at night and I don't want to freeze the entire apartment with a 14畳 aircon. However, I'm not sure option 2 would actually work without true doors.

Thanks for reading my novel.