Beadboard and shlplap in the same (small) space will be way too much. I'd avoid doing either of these on the ceiling-- with only 7', it risks the ceiling seeming much lower and the space appearing more cramped. I'd do a clean white beadboard wainscoting halfway up the walls, an interesting but bright color for the rest of the walls and then white ceilings.

Interesting art on plain walls on your style home would be lovely for a second floor. I wouldn’t do either wood option. Just opening a can of worms in this house.

If you want something, you could just run a chair rail to divide wall. But here are some inspirational photos

Definately no ceiling wood of either choice.

Resist the impulse to add inappropriate tutus and hair bows to a home whose hallmark is simplicity. “Adding interest” should be avoided at all costs. It yields terrible results. Be happy that it’s a great classic pair of jeans and button down shirt.