Settings in style properties should work for these buttons too. It works fine on my side. Maybe it is overwriting something (from extra.less?).
You can do it manually with this in your extra.less template:
Less:
@media (min-width: @xf-responsiveMedium) {
.u-bottomFixer [data-notice-id="-1"] {
left: auto;
right: 20px;
}
}