Sony is a manufacturer, doesn't apply.
THX is just a standard for audio/visual quality, apples and oranges compared to IMAX.
Of the three you listed, only IMAX is actually a format. It's physically different equipment, 70mm 4:3 if I remember correctly, with high frame rate.
An IMAX theater usually has a screen that fills most of your field of vision. Instead of a rectangle at the front of the theater, imagine a screen that wraps almost around your whole vision, now put a super clear picture on it and film someone flying through the Grand Canyon, and it's like you're really there.
Some theaters will occasionally screen a normal movie on an IMAX screen, but it's usually disappointing because of the grain. For an experience worth having, watch an actual IMAX presentation (usually documentaries) on a subject you like and you will be blown away.