I really like the look too. However, I wonder how difficult it is to keep it clean looking,esp. when it is painted white? With air conditioning I suppose dust isn't quite as big of a problem. I have white trim in my bedroom and a creamy white in the kitchen, and the baseboards are the worst to keep grime-free; luckily the kitchen is small so I am able to take a cleaning rag to it more frequently. The bedroom is a different story and the dust on baseboard behind furniture is a challenge because the dusting wand doesn't always do a good job without moving all the furniture out from the wall. I would love the board & batten in my library, stained.

Tib...we had Certainteed. Many boards cracked. The co replaced the boards. We paid for the labor to replace them. They didn't match due to fading. House had to be repainted. They provided a few buckets of paint, lol. just a headache with all of the warranty issues. Then there was a class action suit that we chose not to participate in....yada, yada, yada. I haven't seen the issues online with the Nichiha and have considered this brand as well. lots of good stuff online about the LP Smart Siding but who really knows about that stuff in a few years. Gotta choose something sooner or later.

All your trim needs to be considered when doing a project like this -- base, casing, window stool and apron. I prefer to have a reveal, or small setback where one component meets another, so in your case, I would hold the stiles and rails forming the paneling back (they would be thinner) from the face of the window casing. This shows a 1/8" step where the base meets the door casing, and a 1/4" step where the paneling stile meets the door casing.

Your room is lovely and it reminds me of the dining rooms in the homes of our early American Presidents. I did not notice the difference in space between the left window/near wall and the right window/near wall. If you put anything there, even a plate, it will throw off the symmetry of that end of the room and call attention to a spatial difference that no one actually notices. Your curtain rods may not be fully extended. I would check that first. Personally, I like the separate curtain rods and think if you pulled the curtains together at the center top and added hold backs right above the wainscoting (easier to repair hardware holes in the wall than to try to cover them up in wainscoting if you should ever want to make a change) it would give the windows a more formal appearance for very little money. You can gently pull a bit of the curtain so it slightly curves as it drapes behind the hold back rather than be pulled straight.