This is difference between the default preference of Firefox 100.0 beta 6 and one of 99.0.1. This diff table is generated with my small script firefox-prefjs-surveyer.

Preference difference
PrefFirefox 99.0.1Firefox 100.0 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-browser&utm_campaign=whatsnew https://www.mozilla.org/%LOCALE%/firefox/%VERSION%beta/releasenotes/?utm_source=firefox-browser&utm_medium=firefox-browser&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.cache.offline.enable true false
browser.contentblocking.features.strict tp,tpPrivate,cookieBehavior5,cookieBehaviorPBM5,cm,fp,stp,lvl2,rp,ocsp tp,tpPrivate,cookieBehavior5,cookieBehaviorPBM5,cm,fp,stp,lvl2,rp,rpTop,ocsp
browser.contentblocking.report.vpn_regions at,be,ca,ch,de,fr,ie,it,my,nl,nz,sg,es,gb,us as,at,be,ca,ch,de,es,fi,fr,gb,gg,ie,im,io,it,je,mp,my,nl,nz,pr,se,sg,uk,um,us,vg,vi
browser.contentblocking.state-partitioning.mvp.ui.enabled true undefined
browser.history.wireframeAreaThreshold undefined 50
browser.newtabpage.activity-stream.telemetry.ut.events false true
browser.promo.focus.disallowed_regions undefined cn
browser.promo.focus.enabled undefined true
browser.sessionstore.max_write_failures 5 undefined
browser.soft_reload.only_force_validate_top_level_document false true
browser.startup.upgradeDialog.enabled false true
devtools.enabled true undefined
devtools.theme.show-auto-theme-info true undefined
dom.IntersectionObserver.enabled true undefined
dom.IntersectionObserverExplicitDocumentRoot.enabled true undefined
dom.events.asyncClipboard true undefined
dom.image-lazy-loading.root-margin.bottom 300.0 100.0
dom.image-lazy-loading.root-margin.bottom.percentage false true
dom.image-lazy-loading.root-margin.left 300.0 100.0
dom.image-lazy-loading.root-margin.left.percentage false true
dom.image-lazy-loading.root-margin.right 300.0 100.0
dom.image-lazy-loading.root-margin.right.percentage false true
dom.image-lazy-loading.root-margin.top 300.0 100.0
dom.image-lazy-loading.root-margin.top.percentage false true
dom.ipc.processCount.webLargeAllocation 10 undefined
dom.largeAllocation.forceEnable false undefined
dom.largeAllocationHeader.enabled true undefined
dom.origin-trials.enabled undefined false
dom.origin-trials.test-key.enabled undefined false
dom.streams.pipeTo.enabled false true
dom.streams.readable_stream_default_controller.enabled false true
dom.streams.readable_stream_default_reader.enabled false true
dom.streams.writable_streams.enabled false true
dom.webmidi.enabled false true
dom.window.content.untrusted.enabled true false
dom.window.sidebar.enabled true false
editor.initialize_element_before_connect undefined true
extensions.InstallTrigger.enabled undefined true
extensions.InstallTriggerImpl.enabled undefined true
extensions.formautofill.creditCards.heuristics.confidenceThreshold undefined 0.5
extensions.formautofill.creditCards.heuristics.mode undefined 0
extensions.formautofill.creditCards.supportedCountries US,CA,UK,FR,DE US,CA,GB,FR,DE
extensions.webcompat-reporter.enabled false true
general.useragent.forceVersion100 false undefined
general.useragent.handledVersionExperimentEnrollment false undefined
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.webgpu.force-enabled undefined false
intl.multilingual.aboutWelcome.languageMismatchEnabled false true
intl.multilingual.liveReload false true
javascript.options.wasm_exceptions undefined true
javascript.options.wasm_simd_wormhole undefined false
layout.css.container-queries.enabled undefined false
layout.css.content-visibility.enabled undefined false
layout.css.grid-item-baxis-measurement.enabled false true
layout.css.moz-locale-dir.content.enabled false undefined
layout.css.moz-lwtheme.content.enabled false undefined
layout.css.overflow-moz-hidden-unscrollable.enabled undefined true
layout.dynamic-reflow-roots.enabled false true
layout.selectanchor undefined false
mathml.xlink.disabled true undefined
media.ffmpeg.customized-buffer-allocation false true
media.forcestereo.enabled false true
media.gmp-manager.checkContentSignature undefined true
media.peerconnection.mtransport_process false true
media.rdd-process.max-crashes undefined 2
media.webrtc.platformencoder.sw_mft undefined true
network.cache.frecency_array_check_enabled false true
network.cookie.noPersistentStorage undefined false
network.cookie.sameSite.laxByDefault false true
network.cookie.sameSite.noneRequiresSecure false true
network.cookie.sameSite.schemeful false true
network.dns.port_prefixed_qname_https_rr undefined false
network.http.http2.allow-push undefined true
network.http.http2.chunk-size undefined 16000
network.http.http2.coalesce-hostnames undefined true
network.http.http2.default-concurrent undefined 100
network.http.http2.default-hpack-buffer undefined 65536
network.http.http2.enable-hpack-dump undefined false
network.http.http2.enabled undefined true
network.http.http2.enabled.deps undefined true
network.http.http2.enforce-tls-profile undefined true
network.http.http2.persistent-settings undefined false
network.http.http2.ping-threshold undefined 58
network.http.http2.ping-timeout undefined 8
network.http.http2.pull-allowance undefined 12582912
network.http.http2.push-allowance undefined 131072
network.http.http2.send-buffer-size undefined 131072
network.http.http2.timeout undefined 170
network.http.http2.websockets undefined true
network.http.referer.disallowCrossSiteRelaxingDefault false true
network.http.referer.disallowCrossSiteRelaxingDefault.pbmode.top_navigation undefined true
network.http.referer.disallowCrossSiteRelaxingDefault.top_navigation undefined false
network.http.spdy.allow-push true undefined
network.http.spdy.chunk-size 16000 undefined
network.http.spdy.coalesce-hostnames true undefined
network.http.spdy.default-concurrent 100 undefined
network.http.spdy.default-hpack-buffer 65536 undefined
network.http.spdy.enable-hpack-dump false undefined
network.http.spdy.enabled true undefined
network.http.spdy.enabled.deps true undefined
network.http.spdy.enabled.http2 true undefined
network.http.spdy.enforce-tls-profile true undefined
network.http.spdy.persistent-settings false undefined
network.http.spdy.ping-threshold 58 undefined
network.http.spdy.ping-timeout 8 undefined
network.http.spdy.pull-allowance 12582912 undefined
network.http.spdy.push-allowance 131072 undefined
network.http.spdy.send-buffer-size 131072 undefined
network.http.spdy.timeout 170 undefined
network.http.spdy.websockets true undefined
network.jar.record_failure_reason false true
network.predictor.enable-prefetch false true
network.process.enabled false true
privacy.annotate_channels.strict_list.enabled false true
security.disallow_non_local_systemprincipal_in_tests undefined false
security.intermediate_preloading_healer.enabled false true
security.onecrl.maximum_staleness_in_seconds 108000 undefined
security.pki.crlite_mode 1 3
security.remote_settings.crlite_filters.enabled false true
security.secure_connection_icon_color_gray true undefined
services.sync.engine.bookmarks.validation.enabled undefined true
services.sync.engine.passwords.validation.enabled undefined true
toolkit.telemetry.enabled false true
widget.gtk.overlay-scrollbars.enabled false true