If you want to customize your browser (as far as using your own CSS) you can try Vivaldi. I've been using it for years and after the 3.7 update it feels fast and snappy (at least on my computer). It has tons of custom settings around tabs, commands, windows, toolbars, etc.

At least on Linux it gets out of my way quite nicely. Things like easily accessible Profiles help me quite a lot with my workflow.

If you're really strict about privacy there are browsers like ungoogled-chromium, Bromite (Android) and Orion Browser (only on Mac, iOS) which promise 0 telemetry, connections against their services, etc. Brave is nice but has connections against their services (internal addon updates, safe browsing, updates).