You can generally mix-n-match to suit your requirement. In general, verify the tow vehicle can handle the intended load, pick the hitch, select a drawbar that fits the hitch's receiver and has the correct drop/rise, and then pick a towball that fits the trailer's coupler and the drawbar.
For example, let's say you want a
Class II hitch with a 1-1/4" receiver. Here's a
Class II drawbar (may or may not be the correct rise/drop) for a 1-1/4" receiver. This drawbar accepts a towball with a 3/4" shank diameter. Here's a
1-7/8" towball with a 3/4" shank.
Don't attach a towball with a 3/4" shank to a drawbar with a 1" mounting hole.
If you later decide to tow a trailer with a 2" coupler, you change the tow ball to a
2" diameter / 3/4" shank model, or get the new ball and a new drawbar.
Finally, remember that the maximum trailer weight is limited by the vehicle tow spec, the hitch, the drawbar, or the tow ball, whichever has the lowest rating.
HTH,
Jim / crewzer