Indeed, lag and server stability is the main reason for suggesting a return to Old Azeroth. You can also gain a small rested bonus, and are not at risk of being attacked.
Dalaran will not be an option at the very start, because nobody will have high enough level to enter the city (portals, summons, etc still require someone to level a little).
Overall, fishing open water in northrend is a good option if the servers are good enough to allow it. Fish inland open water. Pymgy Suckerfish will be popular with Alchemists. Plus, almost all the other fish can be cooked into something "nice" eventually. Even the "trash fish", Bonescale Snapper can be cooked into a +Hit buff food. The core of the cooking guide suggests inland water in Grizzly Hills or Howling Fjord, because there are slightly more options to cook your catch, but either of the 4 lowest-level zones in Northrend are viable. All require 380 to cast, 475 to stop get-aways. Coastal waters contain too many fish that cannot be cooked, with no simple high-value recipe for the trash fish (Rockfin Grouper).
You can use the quirk where "unnamed" coastal water (zone name, with no sub-zone) contains inland fish, to find suitable water close to the arrival points. For Alliance, Valgarde (Howling Fjord) has inland water, so you can fish right next to the trainer. Or you can sit with the penguins, on the ice opposite the dock in Valiance Keep (Borean) - just don't go into The Frozen Sea area. You can watch everyone else arriving on the boat.
Horde are best avoiding Borean Tundra, because the inland water near Warsong Hold will be a popular questing area, and the nearest unnamed coast is probably close to Coldarra, wasting a few minutes of travel/disorientation. Instead travel a short distance north from Vengeance Landing (Howling Fjord), along the coast. There are no Alliance quests in that area, so it should be "safe" on PvP realms. Again, just be careful you do not wander into The Frozen Sea.