Can I set up the multiple-line box to auto-resize in display or edit mode? I have enabled the "Resize at runtime" option to Yes.
do you mean to resize width of controls?
if so, then, afaik, 'resize at runtime' is only meant for vertical resizing (which doesn't seem to be your need)
automatic horizontal resizing for single controls you could achieve with some custom CSS, but to achieve some consistent appearance of several controls together might be a bit tricky.