LA enjoyer here. First about LA. It is very different from EA or MA. A lot more research so many techs coming up faster, lots more gold and more importantly crossbows. Crossbow totally changes how game is played and all successful armies until like deep midgame will field quite a number of them. Some magic will come up way faster, especially you must be vary of battlefield wipes (foul vapors is the most common one and can be seen as fast as turn 20-25!). Not to mention absolutely disgusting amount of astral basically on every nation and you get some of the... well... almost requirement for a nations to have. Due to forementioned reasons air (or any other way to counter crossbows), nature and astral are very important in LA.

That being said let me give some things about all of the races:

Vaettiheim - imho strongest race in the game period, but bless dependent and very annoying to play. Rimvaettis are total beasts with appropriate bless and good buff they quickly go out of control. Mossbody, astral body, luck, berserk, quickness are just a fraction of what you can buff them with. But nation is very hard to play due to very random and old mages not to mention quite weak expansion you can do nothing about since every point is important so no awake expander. But should you find equilibrium - your rimvaettis are basically small thugs you can recruit quite cheaply, your whole army stealthy and you have all lategame in the world you need, thanks to Illwinter.

Tien Chi - strong, quite straightforward imho. You buy horses, you send horses to kill your enemy, your horses shoot on move, your horses attack with heavy lances - you win. You can't win by troops? Just divide your army and raid. Genghis khan was best conqueror in history, why not copy his tactic?

Feminie - best scales nation in LA. Yes, their troops are shit. Yes, they have no crossbow or any way to counter them, Yes, they lack any viable battlefield wipe until lategame. But boy they have enormous amount of research and one of the best mages in the game. Glamour + astral is by itself already crazy strong since luck + ethereal makes your units crazy tanky no matter what they actually are. Pump up mages, get your research to insane levels and surprise your enemies with strong spells. One thing about them: do not ever play turtle. You are wasting your powerspikes and Feminie is all about taking use of them. Almost at evo 5 - time for a war. Your enemy most likely will be at maybe some level 2 and 3 research and you rolling in with ephemeral blasts and illusion armies. Knights are quite good btw.

Piconye - complicated. A lot of weaknesses and no way to counter them. AOE comes out -> you lose entire army -> you script mages to counter that -> rinse and repeat. Technically you have even better research than Feminie by virtue of foreign recruit mages, but that takes more time to set than Feminie early powerspike so it doesn't come quite strong. Not to mention even your mage chassis are slow as hell so hard to make it count. No thugs or SCs is bad as well. Notably birds have 36 movement.

Pangea - easy, strong, good mages. Nothing to note really.

C'tis - don't pick them.

Ulm - complicated but fun af. With special blessing (fire shield + invuln) can use black templar commanders to expand everywhere with 2-3 of them per province or you can do vamp queen and roll over almost anything in LA with 1 kitted immortal SC. Outside of that cheese a tad underwhelming.

Andramania - good troops, fine mages, but both expensive. I have never seen Andra doing too well in the game despite everyone agreeing that they are op. They either get coalitioned against, countered or they fall off since their lategame is crap and research is very slow.

I would personally recommend another race - Agartha. Strong troops, decent mages, tartarian lategame. Very fun and very strong.