Uppercase, title case and sentence can all be used in the same application. But if you are using title case for headings, all headings need to be in title case. Likewise, you can use sentence case for paragraphs. Use uppercase for standout texts only. The most important thing is consistency.
<p class="tts">The quick brown fox ...</p>
The quick brown fox jumps over the lazy dog.
<p class="ttt">The quick brown fox ...</p>
The quick brown fox jumps over the lazy dog.
<p class="ttu">The quick brown fox ...</p>
The quick brown fox jumps over the lazy dog.
.tts:first-letter { text-transform: uppercase; } .ttt { text-transform: capitalize; } .ttu { text-transform: uppercase; }