Since people who are overweight generally have less testosterone, will they develop late or less?

Yes, often. It's complicated but what happens in normal weight boys at puberty is a huge surge of testosterone to make their penis and testicles enlarge, muscles and hair to grow and voice to deepen. In obese kids, a lot of the testosterone made gets converted to estrogen by an enzyme made in fat cells. The more fat cells, the higher estrogen levels and this lowers the bioavailable testosterone.