Stock CFLAGS, yes. No changes to CPU governors or Ethernet settings from whatever "stock" sets.
Here's an example diffconfig (EFI enabled with https://github.com/openwrt/openwrt/pull/1968, "build_details" is a local package that captures details of my source tree in the image)
CONFIG_TARGET_x86=y
CONFIG_TARGET_x86_64=y
CONFIG_TARGET_x86_64_Generic=y
CONFIG_DEVEL=y
CONFIG_BUSYBOX_CUSTOM=y
CONFIG_BUILD_LOG=y
CONFIG_BUSYBOX_CONFIG_FEATURE_EDITING_SAVEHISTORY=y
CONFIG_BUSYBOX_CONFIG_FEATURE_REVERSE_SEARCH=y
CONFIG_BUSYBOX_CONFIG_FEATURE_VERBOSE_CP_MESSAGE=y
CONFIG_CCACHE=y
CONFIG_DOWNLOAD_FOLDER="/home/jeff/devel/openwrt_dl"
CONFIG_EFI_IMAGES=y
CONFIG_NGINX_HEADERS_MORE=y
CONFIG_NGINX_HTTP_ACCESS=y
CONFIG_NGINX_HTTP_AUTH_BASIC=y
CONFIG_NGINX_HTTP_AUTOINDEX=y
CONFIG_NGINX_HTTP_BROWSER=y
CONFIG_NGINX_HTTP_CACHE=y
CONFIG_NGINX_HTTP_CHARSET=y
CONFIG_NGINX_HTTP_EMPTY_GIF=y
CONFIG_NGINX_HTTP_FASTCGI=y
CONFIG_NGINX_HTTP_GEO=y
CONFIG_NGINX_HTTP_GZIP=y
CONFIG_NGINX_HTTP_LIMIT_CONN=y
CONFIG_NGINX_HTTP_LIMIT_REQ=y
CONFIG_NGINX_HTTP_MAP=y
CONFIG_NGINX_HTTP_MEMCACHED=y
CONFIG_NGINX_HTTP_PROXY=y
CONFIG_NGINX_HTTP_REFERER=y
CONFIG_NGINX_HTTP_REWRITE=y
CONFIG_NGINX_HTTP_SCGI=y
CONFIG_NGINX_HTTP_SPLIT_CLIENTS=y
CONFIG_NGINX_HTTP_SSI=y
CONFIG_NGINX_HTTP_UPSTREAM_HASH=y
CONFIG_NGINX_HTTP_UPSTREAM_IP_HASH=y
CONFIG_NGINX_HTTP_UPSTREAM_KEEPALIVE=y
CONFIG_NGINX_HTTP_UPSTREAM_LEAST_CONN=y
CONFIG_NGINX_HTTP_USERID=y
CONFIG_NGINX_HTTP_UWSGI=y
CONFIG_NGINX_NAXSI=y
CONFIG_NGINX_PCRE=y
CONFIG_OPENSSL_ENGINE=y
CONFIG_OPENSSL_OPTIMIZE_SPEED=y
CONFIG_OPENSSL_WITH_ASM=y
CONFIG_OPENSSL_WITH_CHACHA_POLY1305=y
CONFIG_OPENSSL_WITH_CMS=y
CONFIG_OPENSSL_WITH_DEPRECATED=y
CONFIG_OPENSSL_WITH_ERROR_MESSAGES=y
CONFIG_OPENSSL_WITH_PSK=y
CONFIG_OPENSSL_WITH_SRP=y
CONFIG_OPENSSL_WITH_TLS13=y
CONFIG_OPENVPN_openssl_ENABLE_DEF_AUTH=y
CONFIG_OPENVPN_openssl_ENABLE_FRAGMENT=y
CONFIG_OPENVPN_openssl_ENABLE_LZ4=y
CONFIG_OPENVPN_openssl_ENABLE_LZO=y
CONFIG_OPENVPN_openssl_ENABLE_MULTIHOME=y
CONFIG_OPENVPN_openssl_ENABLE_PF=y
CONFIG_OPENVPN_openssl_ENABLE_PORT_SHARE=y
CONFIG_OPENVPN_openssl_ENABLE_SERVER=y
CONFIG_OPENVPN_openssl_ENABLE_SMALL=y
CONFIG_PACKAGE_build-details=y
CONFIG_PACKAGE_ca-bundle=y
CONFIG_PACKAGE_diffutils=y
CONFIG_PACKAGE_ethtool=y
CONFIG_PACKAGE_findutils=y
CONFIG_PACKAGE_findutils-find=y
CONFIG_PACKAGE_findutils-locate=y
CONFIG_PACKAGE_findutils-xargs=y
CONFIG_PACKAGE_git=y
CONFIG_PACKAGE_grub2-efi=y
CONFIG_PACKAGE_htop=y
CONFIG_PACKAGE_i2c-tools=y
CONFIG_PACKAGE_ip-bridge=y
CONFIG_PACKAGE_ip-full=y
CONFIG_PACKAGE_iperf3=y
CONFIG_PACKAGE_iptables-mod-conntrack-extra=y
CONFIG_PACKAGE_iptables-mod-ipopt=y
CONFIG_PACKAGE_irqbalance=y
CONFIG_PACKAGE_jansson=y
CONFIG_PACKAGE_kmod-crypto-crc32c=y
CONFIG_PACKAGE_kmod-crypto-hash=y
CONFIG_PACKAGE_kmod-fs-ext4=y
CONFIG_PACKAGE_kmod-fs-vfat=y
CONFIG_PACKAGE_kmod-ifb=y
CONFIG_PACKAGE_kmod-ipt-conntrack-extra=y
CONFIG_PACKAGE_kmod-ipt-ipopt=y
CONFIG_PACKAGE_kmod-ipt-raw=y
CONFIG_PACKAGE_kmod-lib-crc16=y
CONFIG_PACKAGE_kmod-nls-base=y
CONFIG_PACKAGE_kmod-nls-cp437=y
CONFIG_PACKAGE_kmod-nls-iso8859-1=y
CONFIG_PACKAGE_kmod-nls-utf8=y
CONFIG_PACKAGE_kmod-sched-cake=y
CONFIG_PACKAGE_kmod-sched-core=y
CONFIG_PACKAGE_kmod-tun=y
CONFIG_PACKAGE_kmod-udptunnel4=y
CONFIG_PACKAGE_kmod-udptunnel6=y
CONFIG_PACKAGE_kmod-wireguard=y
CONFIG_PACKAGE_less=y
CONFIG_PACKAGE_libacl=y
CONFIG_PACKAGE_libattr=y
CONFIG_PACKAGE_libcap=y
CONFIG_PACKAGE_libelf=y
CONFIG_PACKAGE_libi2c=y
CONFIG_PACKAGE_libiwinfo=y
CONFIG_PACKAGE_libiwinfo-lua=y
CONFIG_PACKAGE_liblua=y
CONFIG_PACKAGE_liblucihttp=y
CONFIG_PACKAGE_liblucihttp-lua=y
CONFIG_PACKAGE_liblzo=y
CONFIG_PACKAGE_libmnl=y
CONFIG_PACKAGE_libncurses=y
CONFIG_PACKAGE_libopenssl=y
CONFIG_PACKAGE_libopenssl-conf=y
CONFIG_PACKAGE_libpcap=y
CONFIG_PACKAGE_libpcre=y
CONFIG_PACKAGE_libpopt=y
CONFIG_PACKAGE_libubus-lua=y
CONFIG_PACKAGE_libusb-1.0=y
CONFIG_PACKAGE_lua=y
CONFIG_PACKAGE_luci-app-firewall=y
CONFIG_PACKAGE_luci-app-openvpn=y
CONFIG_PACKAGE_luci-app-sqm=y
CONFIG_PACKAGE_luci-app-wireguard=y
CONFIG_PACKAGE_luci-base=y
CONFIG_PACKAGE_luci-lib-ip=y
CONFIG_PACKAGE_luci-lib-jsonc=y
CONFIG_PACKAGE_luci-lib-nixio=y
CONFIG_PACKAGE_luci-mod-admin-full=y
CONFIG_PACKAGE_luci-mod-network=y
CONFIG_PACKAGE_luci-mod-status=y
CONFIG_PACKAGE_luci-mod-system=y
CONFIG_PACKAGE_luci-proto-ipv6=y
CONFIG_PACKAGE_luci-proto-ppp=y
CONFIG_PACKAGE_luci-proto-wireguard=y
CONFIG_PACKAGE_luci-ssl-nginx=y
CONFIG_PACKAGE_luci-theme-bootstrap=y
CONFIG_PACKAGE_nginx-mod-luci-ssl=y
CONFIG_PACKAGE_nginx-ssl=y
CONFIG_PACKAGE_openssl-util=y
CONFIG_PACKAGE_openvpn-openssl=y
CONFIG_PACKAGE_procps-ng=y
CONFIG_PACKAGE_procps-ng-free=y
CONFIG_PACKAGE_procps-ng-kill=y
CONFIG_PACKAGE_procps-ng-pgrep=y
CONFIG_PACKAGE_procps-ng-pkill=y
CONFIG_PACKAGE_procps-ng-pmap=y
CONFIG_PACKAGE_procps-ng-ps=y
CONFIG_PACKAGE_procps-ng-pwdx=y
CONFIG_PACKAGE_procps-ng-skill=y
CONFIG_PACKAGE_procps-ng-slabtop=y
CONFIG_PACKAGE_procps-ng-snice=y
CONFIG_PACKAGE_procps-ng-tload=y
CONFIG_PACKAGE_procps-ng-top=y
CONFIG_PACKAGE_procps-ng-uptime=y
CONFIG_PACKAGE_procps-ng-vmstat=y
CONFIG_PACKAGE_procps-ng-w=y
CONFIG_PACKAGE_procps-ng-watch=y
CONFIG_PACKAGE_rpcd=y
CONFIG_PACKAGE_rpcd-mod-rrdns=y
CONFIG_PACKAGE_rsync=y
CONFIG_PACKAGE_sqm-scripts=y
CONFIG_PACKAGE_tc=y
CONFIG_PACKAGE_tcpdump-mini=y
CONFIG_PACKAGE_terminfo=y
CONFIG_PACKAGE_usbutils=y
CONFIG_PACKAGE_uwsgi-cgi=y
CONFIG_PACKAGE_uwsgi-cgi-luci-support=y
CONFIG_PACKAGE_wireguard=y
CONFIG_PACKAGE_wireguard-tools=y
CONFIG_PACKAGE_zlib=y
CONFIG_RSYNC_acl=y
CONFIG_RSYNC_xattr=y
CONFIG_RSYNC_zlib=y