Personally, I would lay it in the direction you want in the bigger area, and keep that same direction everywhere. If you choose to change direction, you do not need "a trim strip or something to cover the transition" unless you have a terrible installer. I have changed direction in rooms vs hallways. You need to specially cut a groove in the first piece, or cut a special tongue piece to fit the 2 grooves together, depending on the direction you are installing. You just need to make the ends of one piece fit into the side of the next piece, and it takes a bit of conscious joinery. If your installer is some joe with no carpentry skills, he might just leave a gap and cover it with a speed bump. Don't let that guy install your floors. As for the direction of the joists, this was true back in the day, when you wouldn't have subfloor, or your subfloor would be in planks, so you'd have to be sure to run the planks in the opposite direction of whatever was underneath them. Is there a reason to keep doing that nowadays, when most people have 4x8 sheets of plywood as their subfloor?

You have 2x10 joists 16"oc with a 14' span and a 3/4" t&g subfloor? You can lay that floor any darn way you want to. If you are ultra fearful of running it parallel to joist, blocking every 24" would be plenty. And the blocking would not need to be full joist thickness. A 2x6 would do fine, it would just need to be placed directly against the subfloor.

The only time to violate the unwritten rule of running wood flooring with the length of a room might be if a majority of doors and windows were located on the long walls. Although the book says to run flooring perpendicular to the underlying joists, I have violated that rule many times with no adverse effects. Run it the way it looks best to you with the foreknowledge that you may be running it with the joist direction and possibly creating an unorthodox and potentially troublesome install.

If you are working with wood-joist construction, then you must run the wood perpendicular to the joists. If this is concrete construction, then you run the LONG edge of the planks in the same direction as the LONG RUN of the condo. Without knowing how your condo is built, that's as much advise as we can give. Photos would help.