I’ve been an enterprise UI/UX design engineer for over 20 years and have seen all kinds of different “themes” and designs come and go. The most important things to remember are: 1) Do not do anything that the user does not expect. Animated labels that shift from placeholders to labels are not good. I hate these because they are distracting and confusing. 2) Properly define the boundaries of your fields. The underline is all cutesy and minimalist, but it’s also confusing … where does the cursor go??? Using shading is a good way to define the minimalist field; and there is nothing wrong with clean borders.