18AWGX2C wire to standard breadboard

If you are connecting to actual female pins, it does help to have the right sized male pin crimped onto your jumper wires. But if you're just using them on a breadboard, bare wire ends are fine. Just make sure to cut the wire with diagonal cutters, not scissor-type cutters, so that you get a nice pointy end. The shearing action of scissor type cutters can sometimes roll the wire end enough to make it snag in the breadboard.

If I understand right you have some breakout boards with 1mm holes, and are wanting to find a suitable header to solder on in order to plug them into your breadboard and use them in a circuit.

If the above is correct (correct me if not) then simply use standard unshrouded 2.54mm pitch headers, the fact that the holes in the breakout board are 1mm won't matter for soldering purposes.

If it's a test jig you want, then the pogo pins (and proper PCB) are probably the way to go.