Are forms with infield top aligned labels better than left aligned forms that provide a clear scan line?

1. Which label alignment on forms is ideal for complex forms?
2. Should I use floating labels?

Which label alignment on forms is ideal for complex forms?

Top aligned and inside field labels are ideal for forms because they're easier to scan than side labels.

Should I use floating labels?

Summary. Please don't use “floated labels” or “labels as placeholders” technique; it can break the user experience for a large variety of reasons. Use the label element and placeholder attribute as intended. Use CSS to ensure placeholder text has adequate color contrast.