Hello, I am trying to figure out how to modify the size of the text in the single/multiline text box? If my users do not format the text when populating the form, is there a way to set it a size automatically? And why doesn't the background color apply to the text boxes? How can I align the background color for all the fields? Some fields display the box with background color, while others only display the text.
Which form designer are you using?
In general only in classic designer you will have enough power to control everything. In Responsive Designer and New Responsive Designer you will have to go with what the Styles tab allows you.
In general I suggest using the new responsive designer. You can use the control fill style to set up background colors for all fields.
The designer in my screenshot is the new responsive designer. The first version of the responsive designer was very limited. In o365 the new responsive designer should be available. If it's not then can you try to update the Nintex Forms app on your site?