Mr Slim Air Conditioning Mr. Slim (ductless Air Conditioning) - Do They Work Fine?

Mr. Slim (ductless air conditioning) - Do they work fine? - mr slim air conditioning

Really a cooling solution in the house of my 1-1/2. It's too hot in summer.
They said that Mr. Slim - 12000 BTU in the room above works for my house (650 m²). - Basement is not included, it's okay, no need for refrigeration.
What do you think?
It will install a unit updsair the house is cool and moisture will help, even from one room to another?
Below is an open concept, with no doors) without walls (kitchen + living room + dining room.

I'm not sure that Mr. Slim is so powerful. I mean, I feel that only work for a single room.

Or a Mr. Slim will receive a 15,000 BTU or more?

It is too expensive to run in the summer? I live in Toronto (very hot and humid in summer)

Thank you!