Usually baseboards were stained the colour of the floor to trick the eye into extending the floor space. If you have a small room worth sticking to this guideline, but if not feel free to paint colour of wall or a different colour such as white or black.

How do you arrange cords when a desk is floated in the room?

I like white especially if you have other areas with different flooring (like carpeted bedrooms) and they have white trim. I love the contrast of our walnut floors and white trim.

The cord problem is a challenge. You almost need the desk angled with a corner near the wall rather than completely floating.

If there is access to the structure below a competent electrician can install a floor outlet for your desk location. These come in bronze (the material, not the finish) and have a solid cap that allows traffic and or furniture to be placed on them when not in use. We mount them flush to the flooring so that they are not a trip hazard. Oh...and I like both white and stained baseboards but prefer contrast....you spend money on both, shame to lose out on either! I do appreciate a shoe moulding at the base to floor transition to match the floor.

How high on the wall does a wall mounted TV go?

It should be at a comfortable level for viewing. Sit in your chairs and look at the wall where the TV will hang. Note the point that is comfortable. Too high and you get a crick in your necks! I am not aware of a set formula, because distance from TV varies depending on your room.