Manjaro has been one of the worst Arch-based distros I have used so far. It broke constantly, where normal Arch wouldn’t. Also, it’s just not a good look when their website certificate runs out and they tell users to turn back the clock a few days until they fix it (archive link, changed to this). Also it expired again a year later (archive)
Generally, no. Apt gets its packages from the repositories, so unless (i) your .deb package gets added to those repositories, or (ii) you add a new repository that contains your package, it won’t be updated.