Does the rendered HTML show actual size attributes showing up?
Secondly, I believe that even with inline size attributes, CSS can override those by setting inputs to particular widths. So this might be a non-issue with the size but it would be good to know about the max-lengths for example, since form validators sometimes make use of them.
We use WTForms at work and I’m always wasting time trying to figure out how to add attributes and edge cases I need to them. Generated forms are my enemy. But often I find how a lot of things are defaulted by looking at the main forms classes, so you’d want to look at where Django imports “forms” and see what’s defined in for example the widgets.