I think the DirectRadioButton is a fine change. It does break behaviour for people, but it’s likely that they’re already customising the theming anyway.
I prefer separate patches for separate features. This way, they can be reviewed and committed independently. It’s also easier to do that one change at a time. However, if one change spans multiple files, those should go into a single patch.
To create a diff on several files, you can just pass one or more filenames to the “cvs diff” and “git diff” commands.
(Note: cvs diff and git diff are almost identical to the standard “diff” tool in which options they take.)