This is difference between the default preference of Firefox 123.0 beta 6 and one of 122.0. This diff table is generated with my small script firefox-prefjs-surveyer.

Preference difference
PrefFirefox 122.0Firefox 123.0 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
apz.minimap.enabled undefined false
apz.scrollend-event.content.enabled true undefined
browser.firefox-view.search.enabled false true
browser.firefox-view.virtual-list.enabled false true
browser.newtabpage.activity-stream.telemetry.ut.events false true
browser.ping-centre.log false undefined
browser.ping-centre.telemetry true undefined
browser.search.searchEngineRemoval https://support.mozilla.org/1/firefox/%VERSION%/%OS%/%LOCALE%/search-engine-removal undefined
browser.shopping.experience2023.autoOpen.enabled undefined false
browser.shopping.experience2023.autoOpen.userEnabled undefined true
browser.tabs.cardPreview.delayMs undefined 1000
browser.tabs.cardPreview.enabled undefined false
browser.tabs.cardPreview.showThumbnails undefined true
browser.urlbar.quickactions.enabled undefined true
browser.urlbar.quickactions.showPrefs undefined true
browser.urlbar.shortcuts.quickactions undefined true
browser.urlbar.showSearchTerms.featureGate false true
browser.urlbar.suggest.quickactions undefined true
browser.urlbar.suggest.yelp undefined true
browser.urlbar.trending.featureGate undefined true
browser.vpn_promo.disallowed_regions ae,by,cn,cu,iq,ir,kp,om,ru,sd,sy,tm,tr,ua ae,by,cn,cu,iq,ir,kp,om,ru,sd,sy,tm,tr
cookiebanners.ui.desktop.enabled false true
cookiebanners.ui.desktop.showCallout undefined false
devtools.debugger.javascript-tracing-values undefined false
devtools.inspector.rule-view.focusNextOnEnter undefined true
devtools.inspector.showRulesViewEnterKeyNotice true undefined
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.events.asyncClipboard.clipboardItem false true
dom.events.asyncClipboard.readText false true
dom.forms.always_allow_pointer_events.enabled false true
dom.forms.fieldset_disable_only_descendants.enabled false true
dom.importMaps.enabled true undefined
dom.mouse_event.region.enabled false undefined
dom.security.https_first_schemeless false true
dom.security.setdocumenturi false true
dom.webcomponents.shadowdom.declarative.enabled false true
dom.webidl.crosscontext_hasinstance.enabled false undefined
editor.block_inline_check.use_computed_style false true
editor.inline_style.range.compatible_with_the_other_browsers true undefined
editor.join_split_direction.force_use_compatible_direction undefined
editor.join_split_direction.force_use_traditional_direction undefined
extensions.InstallTrigger.enabled true false
extensions.formautofill.addresses.capture.requiredFields undefined street-address,postal-code,address-level1,address-level2
extensions.formautofill.heuristics.captureOnPageNavigation undefined false
extensions.webcompat-reporter.enabled false true
fission.enforceBlocklistedPrefsInSubprocesses false true
gfx.canvas.accelerated.max-size 0 8192
gfx.canvas.remote.texture-timeout-ms 10000 undefined
identity.fxaccounts.oauth.enabled undefined false
identity.fxaccounts.toolbar.defaultVisible false true
javascript.options.destructuring_fuse undefined true
javascript.options.spectre.jit_to_cxx_calls true false
javascript.options.use_fdlibm_for_sin_cos_tan false true
javascript.options.wasm_moz_intgemm undefined false
javascript.options.watchtower.megamorphic true undefined
layout.css.abs-sign.enabled true undefined
layout.css.color-mix.color-spaces.enabled true undefined
layout.css.color-mix.enabled true undefined
layout.css.exp.enabled true undefined
layout.css.font-display.enabled true undefined
layout.css.grid-subgrid-baselines.enabled undefined false
layout.css.mod-rem.enabled true undefined
layout.css.nan-inf.enabled true undefined
layout.css.round.enabled true undefined
layout.css.trig.enabled true undefined
layout.cursor.disable-for-popups undefined true
layout.dynamic-reflow-roots.enabled false true
layout.spammy_warnings.enabled false undefined
media.allow-audio-non-utility true false
media.ffvpx.mp3.enabled true undefined
media.ffvpx.opus.enabled true undefined
media.ffvpx.vorbis.enabled true undefined
media.ffvpx.wav.enabled true undefined
media.webvtt.pseudo.enabled true undefined
media.webvtt.testing.events true false
memory.phc.enabled false true
network.auth.use_redirect_for_retries false true
network.cookie.prevent_set_cookie_from_multipart undefined true
network.cookie.sameSite.noneRequiresSecure false true
network.dns.native_https_query undefined false
network.dns.native_https_query_win10 undefined false
network.dns.native_https_timeout_android undefined 20000
network.early-hints.enabled false true
network.fetch.cache_partition_cross_origin undefined true
network.http.http2.move_to_pending_list_after_network_change false true
network.http.http3.retry_different_ip_family false true
network.http.useragent.freezeCpu undefined true
network.jar.record_failure_reason false true
network.predictor.enable-prefetch false true
network.protocol-handler.external.firefox undefined false
network.protocol-handler.external.firefox-private undefined false
network.standard_content_type_parsing.response_headers undefined true
pdfjs.enableHighlightEditor false true
plugins.rewrite_youtube_embeds true false
privacy.annotate_channels.strict_list.enabled false true
privacy.clearOnShutdown_v2.cache undefined true
privacy.clearOnShutdown_v2.cookiesAndStorage undefined true
privacy.clearOnShutdown_v2.historyFormDataAndDownloads undefined true
privacy.clearOnShutdown_v2.siteSettings undefined false
privacy.partition.network_state.ocsp_cache false true
privacy.sanitize.useOldClearHistoryDialog undefined true
screenshots.browser.component.last-saved-method undefined download
security.csp.enableNavigateTo false undefined
security.disallow_non_local_systemprincipal_in_tests undefined false
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.tls.enable_kyber undefined false
services.sync.engine.bookmarks.validation.enabled undefined true
services.sync.engine.passwords.validation.enabled undefined true
services.sync.prefs.sync.privacy.clearOnShutdown_v2.cache undefined true
services.sync.prefs.sync.privacy.clearOnShutdown_v2.cookiesAndStorage undefined true
services.sync.prefs.sync.privacy.clearOnShutdown_v2.downloads undefined true
services.sync.prefs.sync.privacy.clearOnShutdown_v2.historyFormDataAndDownloads undefined true
services.sync.prefs.sync.privacy.clearOnShutdown_v2.siteSettings undefined true
svg.nearestAndFarthestViewportElement.enabled true false
toolkit.lazyHiddenWindow true undefined
toolkit.telemetry.enabled false true
ui.new-webcompat-reporter.send-more-info-link false true