>Seriously ? everytime I create a django charfield I try to guess in my head what is the best length for this field to optimize for performance, but sounds like using unlimited length (textfield) field doesn't make any difference. Good news

Pretty much, except if you're using ModelForms you'll end up rendering a different element by default, and the admin (if you use it) will be different. Not really a problem with DRF without the browsable API.