tchunos are inborn and cannot be changed. i dont know how to define tchunos exactly but they are personality types. whether a person is “firey” or placid for example.
middos are different. one is born with a propensity towards certain middos. generosity vs stinginess for example. but these are also influenced by the environment and can be changed with much work.
this is from the Rambam.
you can see tchunos in a child from the moment they are born.