What does The Guns of Northwatch reward?

The Guns of Northwatch gives a choice of Privateer Musket, Sea Dog Britches, 1,550 experience.

Where does The Guns of Northwatch start?

It was picked up in The Barrens.

Its level has not been recorded yet; it shows once a player accepts it with the addon running.

No. The quest exists in Classic Era as well.

World of Warcraft: Forever · quest

A quest in World of Warcraft: Forever in The Barrens and turned in to Captain Thalo'thas Brightsun. Recorded by 1 player running the addon.

Level, giver and objectives show once a player with the addon accepts the quest.

Item	Given	Item level	Vendor sell
Privateer Musket	as a choice	20	10s 38c
Sea Dog Britches	as a choice	20	5s 55c

What does The Guns of Northwatch reward?: The Guns of Northwatch gives a choice of Privateer Musket, Sea Dog Britches, 1,550 experience.
Where does The Guns of Northwatch start?: It was picked up in The Barrens.
What level is The Guns of Northwatch?: Its level has not been recorded yet; it shows once a player accepts it with the addon running.
Is The Guns of Northwatch new in WoW Forever?: No. The quest exists in Classic Era as well.

Source: what players running the addon saw in the quest windows; the quest text itself stays in the game. Every quest seen · The Barrens