If you want to customize your browser's look and feel, SigmaOS is a good choice. It comes with a range of tools to boost productivity, including workspaces to group tabs, vertical tabs for better organization, and a focus mode to help you concentrate. SigmaOS supports Chromium extensions and is built with macOS's SwiftUI programming foundation for a high-performance, native look.
Another useful tool is StylerGPT, a browser extension that customizes ChatGPT's interface with 25 color schemes, 100 high-resolution backgrounds and the ability to upload your own images. It works with Chrome and Edge browsers, so you can make your ChatGPT experience look nicer without sacrificing speed.
If you want a more full-featured browser, Opera Browser has a lot to offer, including Tab Islands for better organization, Chat with AI for more conversational interactions, and a strong security and privacy foundation with a free VPN and ad blocker. It's a good option if you want a fast, secure and feature-rich browser.