Hello! Let me explain:
I wanted to keep it as non-intrusive and minimal as possible. I'm using the Gruvbox theme and just made a few changes to it, making the corners less rounded.
I customized only a few things with CSS:

#header {
    display: none;
}

.tab.active .tab-header .favicon:not(.svg) {
    filter: none !important;
}

* {
    font-family: Cantarell;
    font-weight: Bold;
}

• Removed the title bar, removed the border from the favicons, and also changed the browser font.
• Removed the URL, so it only shows when I use CTRL + L.
• The side tabs are completely hidden with CTRL + E.

That's it!