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From a design perspective I prefer the clean layout of the standard form.
Full width layout:
Responsive layout:
p.s. We should also decide on whether are going to use placeholder text. Usability recommendation is not to use placeholders - see https://www.nngroup.com/articles/form-design-placeholders/. SemanticUI's placeholder deals with a few of these issues and doesn't break the accessibility but doesn't help either (more text is read). If we don't have placeholder text there will be less to translate if we localise the interface and its just less for users to read (I am a less is more person...).
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