Timber with timber can work brilliantly, and it's in keeping with the mid century style you want for your home. This room (below) is a little similar to yours, albeit with less of a pitch to the roof - the large feature lighting helps to break up the expanse of timber on the ceiling. You have a lovely open plan area, so I'd be inclined to use rugs to create zones and a cosy feel. Rugs reduce the impact of a large expanse of flooring material. They have the benefit that you can swap things around to change the look and layout at little cost. I think one trick may be to define your "walls" carefully, and paint these before you go with a new floor. This should give you a sense of whether the timber is overwhelming, and how to balance it. E.g. You might decide it works best to paint the kitchen cupboards to white, to give you a more seamless look and work with your new counter tops. If you want to experiment with the "paint ceiling" approach - gulp, it's a big one!! - then maybe that small section above the kitchen bench, at a different angle to the rest of the roof, could be the spot. It seems to have the same horizontal line as the wall, so even if you don't like the painted look for the whole, you might be able to get away with blending this into the walls. Best of luck!

Love the inspiration pic. What makes it work is the contrast (between horizontal and vertical features) and the balance (between sizes of the different elements). I'd strongly suggesting sketching up your wall, either by hand or electronically and play around with the dimensions of the timber feature to ensure you achieve a good balance between your windows, the timber feature and the matrix board.

Plain ceiling white is a good choice for ceilings. I'm a huge Natural White fan but will consider Whisper White next time I'm painting.

Always seek professional assistance. Be it a colour consultant, designer or a house painter. Always good to bounce your ideas around here as a lot of good advise is given, certainly if you're not sure of where to start. Have a chat to a local house painter, they're the best ones to give solid advice. Paint brands are usually pretty good, certainly the well known ones like Taubmans, Wattyl, Solver, Dulux. Trusted brands been around for decades. Colour consultants are good as they live and breath colour schemes. They can come up with colours to use that the rest of us wouldn't even think of. Terracotta roof is timeless and classic so you're certainly not limited.