yo eman, good to see you back here. There are many ways to apply the new released Launcher3 as system app. Either you copy paste it to root/system/priv-app then reboot. Or change the apk inside sir Tony's mod zip file "System/priv-app/NexusLauncherPrebuilt" and rename the apk into NexusLauncherPrebuilt.apk
or pm me.
---------- Post added at 12:10 PM ---------- Previous post was at 12:05 PM ----------
Just flashed it all the way from NitrogenOS_MicroGAPPS (recommended) "don't reboot yet" flash pixel mod then you do the reboot