For looks of H1 and H2 tags ,if you open template_css.php you woudl see:
h1 {
color:<?php echo $componentHeadingText;?>;
}
h2 {
color:<?php echo $headingText;?>;
}
so if you use custom style you can just use template parameters is you use pre-defined style you can edit /styles/styleX.php to change variable values.
If you want to change html output you must provide overrides in templates html folder, by copying originals from /components folder and making changes.