Will this remote work with the Vivitek QUMI Q3 Plus?

It is sold as a replacement remote for the QUMI Q3 Plus and uses infrared, the same signal type the projector accepts. Check the listing's model list before buying, since universal remotes often cover only listed models.

Does it need pairing or setup?

No. It is a plain IR remote, so it should work once batteries are in, as long as it matches your projector model.

Are the buttons backlit?

No. The buttons are not backlit, so you will need some light to see them in a dark room.

Does it have macro or learning functions?

No. It has no macro function and no display, and it is not a learning remote.

What batteries does it take?

Battery type is not stated in the specs. Most remotes of this kind take two AAA batteries, but confirm on the listing before ordering.

Is it worth buying over the original Vivitek remote?

It covers the basic point-and-press job at a low cost, but it lacks backlighting, a display and macro keys. Choose it as a spare or replacement, not as an upgrade.