Tiragarde Sound and Stormsong Valley are both fairly similar zones, but Stormsong is a little longer, meaning that you might not even have to finish it to hit 120. Tiragarde also comes with a bit of a warning. There are plenty of side quests to do in the zone after you finish the story quests. Don’t do them. It’s not worth the time or the experience you’ll get.
Also Alliance currently has a 30% XP buff in War Mode (Horde has 10%) that will last the reset since that bonus changes reset by reset depending on faction participation in War Mode (so next week might be lower, or stay the same, 30% is the cap limit, it will change from 10% to 30% week by week for both factions depending on representation). It works from 20 onwards, it gives you extra abilities you can earn via leveling to use in PvP.
the guides work great for leveling almost in autopilot, also the zygor guides work great, the only problem is that this 2 companies moved to a monthtly fee payment model for BFA, not worth the money that you are paying if you ended up paying almost the same as the game monthtly subscription. Recently there is a new free addon for leveling in curse addons webpage that do this without the payment, is not as advanced like the pay ones but works. i will leave the link below. We need to support this kind of free addons.
Usually it's best to avoid a lot of instance runs. It is too difficult to account for bad groups, and some instances are too far away with too few quests. Since the experience is very good, it's a good idea to clear nearby instances which have a lot of quests once (Gnomeregan, Deadmines for Alliance). Distant instances with few quests should be avoided (Deadmines for Horde). Low level instances can be cleared by paying or befriending a single high level character. However, since patch 3.3 a new Dungeon group finding system has been implemented, as well as a direct port to dungeons (when entering the group you get ported to the dungeon and back to the same location if you leave it) and thus the travel time to dungeons has been greatly reduced. This makes it a good idea to complete quests or grind while you wait for a group to become available.