Dungeons are always quicker, at least in Classic, TBC and WotLK. I’m sure the it’s the same for Cataclysm (not sure how it is for retail).
In TBC I had a leveling group and I got to 70 in ~1/2 and a half days
I’m not 100% sure but I hear that the stat jump from 80 to ~83 is so large that the greens replace some/all of your gear. I’m not sure if that’s just hyperbole but I keep hearing it.
There’s a site I found that’s either from OG Cata or is from a Pserver that has a detailed list of specs and their rotations along with other misc things (it’s not really finished and seems abandoned but the class portion of it works).
https://www.tauri-veins.com/class_new.php
I made a thread on how to obtain toys and where to obtain pets.
https://us.forums.blizzard.com/en/wow/t/vanity-items-more-toys-for-your-toy-box
https://us.forums.blizzard.com/en/wow/t/cataclysm-pets-and-where-to-find-them
For dungeons I’d assume you’d want high density dungeons but honestly when I do it I’ll probably just be questing while searching for dungeons in RDF, getting exp from two sources.
For professions you can filter by expansion in WoW Head.
https://www.wowhead.com/items/trade-goods?filter=166;4;0
This ^, is a link to what Cataclysm tradegoods there are, which I believe would be the most useful thing to search for. You can also go off by profession.