about:preferences#general: Performance: Uncheck them all. about:preferences#privacy: Disable Firefox telemetry
You have two builtin sound devices: digital and analog. Digital is listed first. You’ve to change the order, cs. firefox and chrome play to the first device only. Try the following: Go to /etc/default/grub and add snd-hda-intel.index=1,0 to the GRUB_CMDLINE_LINUX_DEFAULT line.