Is it bad to have overlapping fingers?

No. If you were born with overlapping fingers, there is nothing wrong with that. If you had trauma and have new overlapping fingers, that can cause difficulty with fine motor use or power grip.
Many fingers have a . Bit of deviation built into them. When u bend your fingers to make a fist together there is some rotation at the joints that keeps them form overlapping. When fingers are bent one by one or if finger is late to bend from being stiff it overlaps a bit and can be normal if however there is a fracture that rotatates the bone then that is a different scenario, that needs to be fixed, .