Although there are no tags available for portfolio, there are categories which do the same job for portfolio items. You can use a shortcode like this –
[show_post_snippets post_type="portfolio" number_of_columns=2 post_count=6 image_size='large' excerpt_count=100 display_title=true display_summary=true show_meta=true hide_thumbnail="false" terms="nature,technology" taxonamy="portfolio_category"]
and for blog posts
[show_post_snippets post_type="post" number_of_columns=2 post_count=6 image_size='large' excerpt_count=100 display_title=true display_summary=true show_meta=true hide_thumbnail="false" terms="tag1,tag2" taxonamy="post_tag"]
But regarding achieving the one column layout you want, you can modify the styling for the particular section in which you place these shortcodes.
But since your requirement is exact styling as that of blog with left date/read more button etc., I see only one option – create a new page template similar to that of template-blog.php with slider at the top (revolution slider shortcode would do), blog content which looks exactly like the regular blog and then at the bottom you would have portfolio shortcode as seen above. I see no other way. Hope this helps.