Keep as many leaves as possible because yield is proportional to the amount of light interception. I'd then cut out a few fruits but not as many as you suggest. Because for one thing once they vine out you won't be able to tell which fruit goes with which plant. You don't want two or more on one plant and none on another.

How much is your total area? That's a lot of plants and you probably need 20 sq ft per plant. 20sqft x 30 plants = 600 sq ft. If you crowd too many plants in a small area some won't have fruit which makes those a weed.

20 square feet per sugar baby watermelon plant? I just researched that number and the only website that suggested that multitude if spacing was a farm that sold watermelons on the market, and they grew full size. Before planting these sugar babies, all of my research said each plant needs at least five feet space, and I have each plant planted five square feet apart. We have a huge yard.

Sugar Babies don't need much if any thinning at all. They are small melons to start with. In fact, you don't want them too large or overmature anyway because they become mealier in texture than they already are. Still, they have a good sweetness and are very reliable. They do vine more than most small melons, but they also are capable of setting more fruit that way.