This is difference between the default preference of Firefox 120.0 beta 6 and one of 119.0. This diff table is generated with my small script firefox-prefjs-surveyer.

Preference difference
PrefFirefox 119.0Firefox 120.0 beta 6
app.normandy.test-prefs.bool undefined false
app.normandy.test-prefs.integer undefined 0
app.normandy.test-prefs.string undefined
app.releaseNotesURL https://www.mozilla.org/%LOCALE%/firefox/%VERSION%/releasenotes/?utm_source=firefox-browser&utm_medium=firefox-desktop&utm_campaign=whatsnew https://www.mozilla.org/%LOCALE%/firefox/%VERSION%beta/releasenotes/?utm_source=firefox-browser&utm_medium=firefox-desktop&utm_campaign=whatsnew
app.releaseNotesURL.aboutDialog https://www.mozilla.org/%LOCALE%/firefox/%VERSION%/releasenotes/?utm_source=firefox-browser&utm_medium=firefox-desktop&utm_campaign=about-dialog https://www.mozilla.org/%LOCALE%/firefox/%VERSION%beta/releasenotes/?utm_source=firefox-browser&utm_medium=firefox-desktop&utm_campaign=about-dialog
app.update.channel release beta
app.update.url.details https://www.mozilla.org/%LOCALE%/firefox/notes https://www.mozilla.org/%LOCALE%/firefox/beta/notes
app.update.url.manual https://www.mozilla.org/%LOCALE%/firefox/new?reason=manual-update https://www.mozilla.org/%LOCALE%/firefox/beta?reason=manual-update
browser.display.focus_background_color #117722 undefined
browser.display.focus_ring_on_anything false undefined
browser.display.focus_ring_style 1 undefined
browser.display.focus_ring_width 1 undefined
browser.display.focus_text_color #ffffff undefined
browser.display.use_focus_colors false undefined
browser.migrate.chrome.get_permissions.enabled undefined true
browser.migrate.content-modal.enabled true undefined
browser.newtabpage.activity-stream.discoverystream.config {"api_key_pref":"extensions.pocket.oAuthConsumerKey","collapsible":true,"enabled":true,"show_spocs":false,"hardcoded_layout":true,"layout_endpoint":"https://getpocket.cdn.mozilla.net/v3/newtab/layout?version=1&consumer_key=$apiKey&layout_variant=basic"} {"api_key_pref":"extensions.pocket.oAuthConsumerKey","collapsible":true,"enabled":true}
browser.newtabpage.activity-stream.system.showSponsored undefined false
browser.newtabpage.activity-stream.telemetry.ut.events false true
browser.privatebrowsing.resetPBM.enabled undefined false
browser.privatebrowsing.resetPBM.showConfirmationDialog undefined true
browser.search.newSearchConfig.enabled undefined false
browser.theme.windows.accent-color-in-tabs.enabled undefined false
browser.topsites.contile.sov.enabled false true
browser.urlbar.bestMatch.blockingEnabled true undefined
browser.urlbar.bestMatch.enabled false undefined
browser.urlbar.eventTelemetry.enabled false undefined
browser.urlbar.merino.enabled true undefined
browser.urlbar.quickactions.enabled undefined true
browser.urlbar.quickactions.showPrefs undefined true
browser.urlbar.quicksuggest.blockingEnabled true undefined
browser.urlbar.quicksuggest.remoteSettings.enabled true undefined
browser.urlbar.quicksuggest.rustEnabled undefined false
browser.urlbar.resultMenu true undefined
browser.urlbar.shortcuts.quickactions undefined true
browser.urlbar.showSearchTerms.featureGate false true
browser.urlbar.suggest.bestmatch true undefined
browser.urlbar.suggest.quickactions undefined true
browser.urlbar.suggest.recentsearches undefined true
browser.urlbar.switchTabs.searchAllContainers undefined false
browser.urlbar.trending.featureGate undefined true
cookiebanners.bannerClicking.pollingInterval undefined 500
cookiebanners.bannerClicking.timeout 3000 undefined
cookiebanners.bannerClicking.timeoutAfterDOMContentLoaded undefined 20000
cookiebanners.bannerClicking.timeoutAfterLoad undefined 5000
cookiebanners.service.enableGlobalRules.subFrames undefined true
cookiebanners.ui.desktop.enabled false true
devtools.performance.recording.features ["js","leaf","stackwalk","cpu","screenshots"] ["js","stackwalk","cpu","screenshots"]
devtools.performance.recording.features.remote ["js","leaf","stackwalk","cpu","screenshots","java"] ["js","stackwalk","cpu","screenshots","java"]
dom.cache.privateBrowsing.enabled undefined false
dom.document.edit_command.contentReadOnly.enabled true false
dom.document.edit_command.insertBrOnReturn.enabled true false
dom.event.keypress.key.allow_lone_surrogate true false
dom.forms.always_allow_pointer_events.enabled false true
dom.forms.fieldset_disable_only_descendants.enabled false true
dom.iframe_lazy_loading.enabled undefined false
dom.security.https_first_schemeless undefined false
dom.w3c_pointer_events.getcoalescedevents_only_in_securecontext undefined false
dom.webgpu.testing.assert-hardware-adapter undefined false
dom.webgpu.workers.enabled undefined false
dom.window.sizeToContent.enabled true false
dom.workers.importScripts.enforceStrictMimeType false true
editor.block_inline_check.use_computed_style undefined true
extensions.InstallTrigger.enabled true false
extensions.formautofill.firstTimeUse true undefined
extensions.formautofill.heuristics.interactivityCheckMode undefined focusability
extensions.script_about_blank_without_permission undefined false
extensions.webcompat-reporter.enabled false true
fission.enforceBlocklistedPrefsInSubprocesses false true
geo.provider.network.url https://www.googleapis.com/geolocation/v1/geolocate?key=%GOOGLE_LOCATION_SERVICE_API_KEY% https://location.services.mozilla.com/v1/geolocate?key=%MOZILLA_API_KEY%
gfx.canvas.remote.allow-in-parent undefined false
gfx.canvas.remote.texture-timeout-ms undefined 10000
gfx.canvas.remote.worker-threads undefined 0
gfx.webrender.blob-images true undefined
image.mem.max_legal_imgframe_size_kb undefined -1
javascript.options.gc_delay.interslice 100 250
javascript.options.use_fdlibm_for_sin_cos_tan false true
javascript.options.wasm_function_references false true
javascript.options.wasm_gc false true
javascript.options.wasm_tail_calls undefined false
layout.css.allow-mixed-page-sizes false true
layout.css.always_underline_links undefined false
layout.css.computed-style.styles-outside-flat-tree false undefined
layout.css.light-dark.enabled false true
layout.css.text-wrap-balance-after-clamp.enabled undefined true
layout.css.text-wrap-balance.enabled undefined false
layout.css.text-wrap-balance.limit undefined 10
layout.css.zoom.enabled undefined false
layout.details.force-block-layout undefined true
layout.dynamic-reflow-roots.enabled false true
media.allow-audio-non-utility true false
media.audiograph.single_thread.enabled true undefined
media.clockdrift.buffering 50 undefined
media.webrtc.platformencoder false true
memory.phc.enabled false true
messaging-system.askForFeedback undefined true
network.auth.use_redirect_for_retries undefined false
network.cookie.sameSite.noneRequiresSecure false true
network.early-hints.enabled false true
network.early-hints.preconnect.enabled false true
network.http.http2.move_to_pending_list_after_network_change undefined false
network.http.useragent.forceRVOnly 109 undefined
network.jar.record_failure_reason false true
network.predictor.enable-prefetch false true
network.url.strict_protocol_setter undefined true
network.websocket.auto-follow-http-redirects false undefined
pdfjs.enableStampEditor false true
print.enabled undefined true
privacy.annotate_channels.strict_list.enabled false true
privacy.fingerprintingProtection.WebCompatService.logLevel undefined Error
privacy.fingerprintingProtection.granularOverrides undefined
privacy.globalprivacycontrol.functionality.enabled false true
privacy.globalprivacycontrol.pbmode.enabled undefined true
privacy.partition.bloburl_per_agent_cluster false undefined
privacy.query_stripping.strip_on_share.enableTestMode undefined false
privacy.query_stripping.strip_on_share.enabled false true
security.disallow_non_local_systemprincipal_in_tests undefined false
security.enterprise_roots.enabled false true
security.remote_settings.crlite_filters.enabled false true
security.ssl3.ecdhe_ecdsa_aes_128_sha true false
security.ssl3.ecdhe_ecdsa_aes_256_sha true false
security.webauth.webauthn_enable_android_fido2 false undefined
services.sync.engine.bookmarks.validation.enabled undefined true
services.sync.engine.passwords.validation.enabled undefined true
svg.nearestAndFarthestViewportElement.enabled true false
toolkit.shopping.environment undefined prod
toolkit.telemetry.enabled false true
ui.mouse.right_click.collapse_selection.stop_if_non_collapsed_selection undefined true
ui.mouse.right_click.collapse_selection.stop_if_non_editable_node undefined false
webgl.gl_khr_no_error undefined true