This is difference between the default preference of Firefox 134.0 beta 10 and one of 133.0.3. This diff table is generated with my small script firefox-prefjs-surveyer.

Preference difference
PrefFirefox 133.0.3Firefox 134.0 beta 10
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.gtk.touchpad_hold.enabled false true
apz.touch_scroll.buffer_max_age undefined 200
browser.contentanalysis.interception_point.clipboard.enabled undefined true
browser.contentanalysis.interception_point.drag_and_drop.enabled undefined true
browser.contentanalysis.interception_point.file_upload.enabled undefined true
browser.contentanalysis.interception_point.print.enabled undefined true
browser.ml.modelCacheMaxSize undefined 4
browser.ml.modelCacheMaxSizeBytes 1073741824 undefined
browser.newtabpage.activity-stream.discoverystream.sections.cards.enabled undefined false
browser.newtabpage.activity-stream.discoverystream.sections.cards.thumbsUpDown.enabled undefined true
browser.newtabpage.activity-stream.discoverystream.sections.enabled undefined false
browser.newtabpage.activity-stream.discoverystream.sections.locale-content-config undefined en-US,en-CA
browser.newtabpage.activity-stream.discoverystream.sections.region-content-config undefined
browser.newtabpage.activity-stream.support.url https://support.mozilla.org/1/firefox/133.0.3/Linux/en-US/new-tab https://support.mozilla.org/1/firefox/134.0/Linux/en-US/new-tab
browser.tabs.groups.dragOverDelayMS undefined 30
browser.tabs.insertAfterCurrentExceptPinned undefined false
browser.tabs.unloadTabInContextMenu undefined false
browser.urlbar.focusContentDocumentOnEsc false true
browser.urlbar.intentThreshold undefined 0.5
dom.forms.autocorrect undefined false
dom.innerSize.rounding 2 1
dom.popup.experimental false true
dom.push.http2.maxRetries 2 undefined
dom.push.http2.reset_retry_count_after_ms 60000 undefined
dom.push.http2.retryInterval 5000 undefined
dom.push.indicate_aesgcm_support.enabled undefined false
dom.security.https_first_add_exception_on_failiure true undefined
dom.security.https_first_add_exception_on_failure undefined true
dom.webgpu.indirect-dispatch.enabled false undefined
dom.webgpu.indirect-draw.enabled undefined false
extensions.ml.enabled undefined false
extensions.webcompat-reporter.enabled false true
extensions.webcompat.smartblockEmbeds.enabled undefined false
identity.fxaccounts.contextParam fx_desktop_v3 oauth_webchannel_v1
identity.fxaccounts.oauth.enabled false true
identity.fxaccounts.toolbar.syncSetup.enabled undefined false
javascript.options.experimental.promise_try undefined true
javascript.options.experimental.regexp_escape undefined true
javascript.options.use_fdlibm_for_sin_cos_tan false true
javascript.options.wasm_disable_huge_memory undefined false
javascript.options.wasm_gc true false
javascript.options.wasm_js_string_builtins false true
javascript.options.wasm_memory64 false true
javascript.options.wasm_tail_calls true false
layout.css.moz-user-modify.enabled false undefined
media.ffmpeg.disable-software-fallback undefined false
media.webrtc.enable_pq_dtls undefined false
media.webrtc.simulcast.vp9.enabled undefined false
network.cookie.CHIPS.lastMigrateDatabase undefined 0
network.cookie.CHIPS.migrateDatabaseTarget undefined 1
network.cookie.cookieBehavior.trackerCookieBlocking undefined true
network.dns.use_override_as_peer_address undefined false
network.fetchpriority.adjustments.link-preload-font.high 0 -10
network.http.http3.force-use-alt-svc-mapping-for-testing undefined false
network.http.referer.sendFromRefresh undefined false
privacy.imageInputTelemetry.enableTestMode undefined false
privacy.resistFingerprinting.randomDataOnCanvasExtract true undefined
privacy.resistFingerprinting.randomization.canvas.use_siphash undefined false
security.external_protocol_requires_permission true undefined
security.pki.certificate_transparency.disable_for_hosts undefined
security.pki.certificate_transparency.disable_for_spki_hashes undefined
toolkit.telemetry.enabled false true