Article background color in Helix3

.view-article article.item, .layout-blog article.item {
	background: #fff;
	padding: 40px 40px 20px 40px;
}

Narrow width in Helix Ultimate (including Featured Image)

#sp-component .article-details {
    max-width: 800px;
    margin: 0 auto;
}

Narrow width in Helix Ultimate (except Featured Image)

.article-header, .article-info		{
	max-width:850px;
	margin:0 auto;
}
[itemprop="articleBody"] {
	max-width:850px;
	margin:0 auto;
}

Body background and custom body max width

.layout-boxed .body-innerwrapper {
    background: #f0f0f0;
	max-width: 1120px;
	margin: 0 auto;
	box-shadow: 0 0 30px rgba(0, 0, 0, 0.4);
}

Frontend edit icon position modification

Open templates\TEMPLATE\html\com_content\article\default.php, go to Line 75 and move out below code from "page-header" class

		<?php if($canEdit && !$this->print) : ?>
			<?php echo HTMLHelper::_('icon.edit', $this->item, $params); ?>
		<?php endif; ?>

Insert below CSS line at custom.css

.article-details .link-edit-article {
    position: inherit;
    right: 0;
    top: 10px;
    float: right;
    padding: 10px 20px;
    background: #f0f0f0;
}