Hey Jonas,
please try this CSS:
body { padding-top: 16px; }
body.page-portfolio { padding-top: 8px !important; }
Concerning the second question: displaying regular posts in the portfolio grid hasn’t been envisaged in Ikebana – it is possible, yet would require some considerable changes in the code of several core template files. I’d recommend trying out the plugin solution first, it does work for me on several instances of WordPress.
Sincerely,
Andrii / Satori Studio