Jock itch (tinea cruris) is a fungus, the same one that causes athlete's foot and scalp ringworm. The groin area is the perfect place for the fungi to grow and cause a fungal infection because it is moist, warm and dark.
The camshaft lift is the resultant net rise of the valve from its seat. The farther the valve rises from its seat the more airflow can be provided, which is generally more beneficial. Greater lift has some limitations.
In other words, let's say the lift at the cam is 0.350 and the theoretical lift at the valve with 1.5:1 rockers is 0.525. Using the 1.3:1 rockers would result in lift at the valve of only 0.455, thus reducing stress at the camshaft/lifter interface during the crucial break in period.