I'm in so cal, and have learned a bit about meshing .. . look for opportunities to change windows to doors, add adjacent open trellis and create a bigger room . .

for napa, i would say, you are wrong about subway, but it might not be your look . . . cottage is easy to do in an older farmhouse or ranch house . . penny tile, chalk painted craigslist finds, slipcovered ikea ektorp furniture, perhaps white painted wood floors. Napa is agrarian, so everytime you reference something you could have seen in a farmhouse 100 years ago, you are on the right track. Horizontal planking on walls, antiqued brick (washed with watered down paint), outdoor furniture can at first be whatever you wanted to off load anyway, painted and recovered with sunbrella, mixed with true outdoor furniture finds like wicker you clean up and paint in your color scheme . .

Long term, splurge on big /good windows and doors, fat trim inside and out, good heating and cooling systems (thus the cross ventilation) .. . great ideabook up now about outdoor patios on a budget . .

And here's one on farmhouse https://www.houzz.com/magazine/roots-of-style-american-farmhouses-pay-tribute-to-regional-traditions-stsetivw-vs~19954037

Is it an existing ranch house style home? What kind of architecture and finishes are you working with? If you haven't started an ideabook here, you can browse photos in the houzz archives and save them there for inspiration. Hope you'll come back and share your project - it sounds wonderful. Napa will be a lovely place to retire . . .