Swing is modulation, or an increase of power (if you will) when you talk on either AM or on either of the sidebands. There's several ways to achieve it...power mic, adjusting the mic gain, adjusting the modulation potentiometer inside the radio....and a few other ways I can't think of.
Too little of it and you might sound like you're talking 10 feet away from the mic, if any at all. Too much and you'll sound like you're eating the mic, crunch crunch and all.
Yes TX is transmit and RX is receive.