When you tug on them, healthy roots feel firm and somewhat springy. Additionally, they should be widely dispersed throughout the soil. While some root tangling is typical, plenty of potting soil should be mixed with the roots.
This fuzz is a natural occurrence that helps the roots pull in moisture and helps the pothos climb vertically. In the wild, aerial roots are designed to cling to rocks and trees, and this fuzzy substance, which looks like plant hair, assists them.
These houseplants can tolerate being slightly rootbound, but the last thing you want is to have your pothos completely rootbound. Pothos need space to grow and thrive.