Picked TikTak'to because of sick micro potential on the battlefield with his upgraded Terradons, Rippers, heroes on Terradons @ recruitment, global +10MA and that he screams his name in passion each time when I click him

. His Vortex spot is very good, his ME spot is meh, but we have KG for that. Also TTT and a group of rippers and you are hard-countering any air unit in the game. My favorite mid game composition with this guy is terradons, rippers, skinks, horned/cold one riders and the carnosaurs.
Already mentioned KroqGar is a strong contender as he is literally the best rush lord of the Lizardmen in vortex campaign solving all of his problems with a button to recruit more Saurus. After few levels your saurus become indestructible and you can do 1v4 stack battles with ease. He has probably the best spot in Vortex campaign and a good spot in ME. Also did I mention I did a Vortex campaign on legendary with 0 unit losses until turn 200, the last ritual?
Mazdamundi was my first try and since it was my first total war game ever I played him on easiest difficulty as well as with tutorial material. He was a very good introduction. I did a few turns on Legendary few years later. Skeggi is a bitch, but rushing them is very rewarding. His Vortex spot is questionable, ME spot meh due to map cut in half. Generally overshadowed by other LLs and Slann of Life if you run a lot of dinosaurs. He has balanced spells, but the campaign feeling is not right.
Nakai was a biggest disappointment for me. Virtually no money during the game, low amount of blessed units, waiting 480239840 turns to get additional unit type, no trading, shitty vassal mechanic, need to launch political UI and cycle through every possible race to beg for money and the fact that every faction declares war on your vassal. I rushed the vortex campaign and won in like 40 turns, but ME is unplayable with this guy. ME is making the things that annoy you in Nakai to the limit: limited amount of friendly races to get money from, snow attrition, even more people declaring war on the vassal because reasons.
Gor-Rok and Tehen are waiting to be played. GR sounds like its possible to do Legendary vortex before Turn 150 due to his rush potential. Tehen sounds like a chore, but also a way to play more Skinks.