All changes to the default Basilisk configuration are listed below.

Configured custom plugin directories in Basilisk-Portable.ini
Other changes to Basilisk-Portable.ini (lines starting with ; are commented out): 
ShowSplash=false
;(multiple instances)
;MOZ_NO_REMOTE=1

Preferences set:
When Basilisk starts show a blank page
Play DRM content
Block pop-up windows - false
Send a signal that you don't want to be tracked
Remember logins for sites - false
Basilisk will use custom settings for history
Remember search and form history - false
Automatically update search engines - false
Never check for updates
Query OCSP responder servers to confirm the current validity of certificates - false

about:config Switches Set:
extensions.blocklist.enabled - false
javascript.options.wasm - true
network.captive-portal-service.enabled - false
network.stricttransportsecurity.preloadlist - false
security.mixed_content.send_hsts_priming - false
browser.newtabpage.directory.ping - blank
browser.newtabpage.directory.source - blank
extensions.systemAddon.update.url - blank
media.gmp-manager.url - blank
dom.ipc.plugins.asyncdrawing.enabled - false
dom.ipc.plugins.flash.disable-protected-mode - true
dom.disable_window_open_feature.location - false
dom.allow_scripts_to_close_windows - true
plugin.scan.plid.all - false
