I bought the least expensive ones that Fred Meyer carries and only when they're on sale. My grandchildren rarely wear them. I have a pair that I wear when I'm on rough ground. Otherwise they just get in the way. One cannot swim efficiently in them. They cause drag.
I see a few toddlers/preschoolers wearing swim shoes at the public pool but I don't think I've ever seen a school age child wearing them. For me the only advantage to wearing them on an even surface is to provide traction and possibly to prevent exposure to athlete's foot in the shower room. I have seen some kids and adults put on swim shoes when exiting the pool.
The least expensive rubber and mesh shoes are of good quality. I've not seen a reason to spend more money.
My grandchildren love to be barefoot. I think that the exposure to various textures is good for their sensory awareness growth. I've not known anyone to get athletes foot in the past 20 or so years. I think the pool staff use good disinfectants. I do recognize the usefulness of prevention by wearing thongs or water shoes.
I've not seen swim socks.