I have used an oil-filled electric heater that looks like a radiator in several houses over the past 10 years. (I have gone through 3, but only because I have moved a lot and some houses did not need one) It works fantastic, keeps the room a wonderful, consistent temperature, doesn't use much electricity and easily stores away in the summer. While you can turn them on and off during a day, they work very well and efficiently if left on all the time. It takes less energy to keep the oil heated than it does to turn the heater off and on a few times a day. I like my rooms very warm and as long as the room had one regular-sized interior door (the heater has heated the bedroom nicely even with the door 1/2 to 3/4 way open, but the more closed the space, the warmer it will be), I haven't needed to use the heater at more than 1/2 way to the highest setting. I live in Colorado, so our winters can be very cold (to give you a reference point for temperature). It also takes a little while to heat up, but once it is warm, the radiant heat seems to fill the room rather than one small area. This is my favorite type of heater I have ever used.

I like baseboards larger than door and window casings. On door casings, I like your idea of same design/different width casings. Except maintain consistency like all doors in the old part of the house have the same narrower width casing. You don't want to look down a hallway, for example, and see different width casings on some than on others.

We need to make the same types of decisions for our baseboards and our door and window trim. A simple 1x8 was suggested for the baseboards (we will have 10' ceilings) but in addition to concerns about dust-collection I might like to incorporate a touch of elegance. The architectural style is barn/farmhouse which has a certain charm in itself but it's also quite masculine with all of the straight lines and right angles (though not as much as Craftsman). Our doors will be 2-panel with square tops, but I'm partial to French Country style and was hoping to incorporate a simple cove or roundover at the tops. The same issue presents with the doors and windows as I like the overall simplicity suggested here but I'm not sure if I want something as stark as some planks nailed to the wall. Suggestions?

Well standard height for A ceiling does not exist, but let’s assume 8ft which is the typical minimum. I would do an 8” baseboard and 5-1/2” crown molding. The larger baseboard will give a more powerful impression.