15" Laptop has a 1920x1080 display that's not quite hidpi. So I'm using layout.css.devPixelsPerPx value in about:config of 1.4, and in GNOME Settings > Accessibility, enable large text.

This does make things a bit too big on the 24" external display which has nearly the same resolution, but it's not distracting. Some websites I use CTRL-+ and CTRL-- to change the scaling, or rather fine tune it, depending on more than +-20% and the rendering gets wonky. Firefox seems to remember this per site even after a relaunch or reboot.

The biggest problem I have is Bluetooth, my mouse is always disconnecting on Linux, dozens of times per day, but the same laptop+mouse rebooted to Windows 10 - no problem.