I remember that! Good lord, that stuff was cheese. Flood was the "This is now a water map" spell, combine with Lizards and it was fun fun fun. Raze ALL shipyards in sight for greater trollololololololo.
My favourite part about it was cancelling it and watching the AI wander back out into the now "de-flooded" zones - only to drown when I cast it again. Also pairing it with three Earth spheres so you could use Lower Terrain to get rid of those pesky hills and mountains that can't be flooded.
The AI definitively could't into enchants - I remember seeing entire armies of enchanted tier 1 crap units and unenchanted heroes and leaders. Why every other swordman needs enchanted weapon, anyway? Then again the AI has mana out of its ass.
Yeah, the issue was more casting points than mana. Enchants are such a weird thing. Like I don't even know how I'd describe when to best use them. It's like there's a certain threshold where T1 units are the best choice, but that very rapidly falls off and you never want to enchant a T1 unit again for the rest of the game. That sort of concept in general is easy to teach an AI. The tough part is teaching it to recognize that falling off point. You could teach the AI to remove enchants on units it was no longer using, but like you said, mana was never the issue for the AI.
Ah yeah, Zephyr Bird cheese! Kill all ranged, leave bird, drawn ftw! Best way to stop a 8-Lord stack or huge army, ever!
Don't forget Dragon/Air Galley cheese on AOW1 too - Air Galley cheese was so bad that in the final Valley of Wonders scenarion in 1, all leaders often get killed by Air Galley Lithuanian Hitmen attacks. If you survive, then its just you vs King Joseph AND Gabriel.
AOW1 and 2 also had Air Galley Hasting, which turned Air Galleys into Airplanes. I think they got like functional 72 movement, you could simply fly across the map casually and leave the AI in the dust. They nerfed it in AOWSM because that was utterly hilariously ridiculous (also because they would become jet planes in the Shadow Realm, lol).
Incarnate Cheese? Pff, Reaper cheese ftw. Ever get approached by a huge, mighty, mega-epic army that could destroy Rome, China and the Hellenic Empire in a week, but they don't have any magic damages whatsoever? One reaper takes care of that. Reaper? More like RAPER!
I also remember casually blowing through armies with Red Dragons in AOW1 too. Althrough to be fair, Orcs in AOW1 were the Cheese Race - strongest level 1 basic infantry, strongest level 2 cavalry, Shredder Bolts, War-freaking-Lords and Red Dragons, they were just ridiculous.
The best Zephyr Bird cheese was the fact that if you position them over certain buildings in a city or watchtower, all ranged attacks would be 100% blocked by obstacles. You could just have your Zephyr Bird sitting there floating over your Barracks while 32 Centaurs fired non-stop, to no avail. IIRC using this exploit in multiplayer games would get you blacklisted - for good reason, haha
AoW 1 also had the legendary Free Moving Dragon Ship exploit - possibly the greatest cheese of all. It turns out that if you cast Free Movement on a ship, it gains the ability to travel on land, as well. As ships were significantly more durable than any land units (for the record, the Dragon Ship has 20 HP, which is more than all but a couple of level 4 units), and Free Movement and Dragon Ships were both level 2, it broke the game very, very quickly.
This works with any ship, and Wind Walking does it as well I believe, but it was known as FMDS just because those were the most common forms. Ballistas were ridiculously powerful in AoW 1 but were held back by being kinda fragile, and super slow. Ships don't suffer from either of those issues, but have the same power. Plus you could also set up a convoy of them as "land ships" to transport your troops quickly across the map.
They were literally a weaker, cheaper, and easier to mass-produce Air Galley that was available to all races. Unlike the Air Galley it was vulnerable to melee attacks, but with 20 HP that wasn't a huge issue.
Orcs were pretty amazing, though. I always felt kind of bad for them because the sheer power of some of their units meant that the others got left out. Orc Assassins and Doom Bats were cool concepts but you never built them because Warlords. Plus they were pretty awful in their own right. Doom Bats were the worst flyers in the game, and Assassins somehow were worse melee fighters than Halfling Rogues. Orc Swordsmen are one of the few instances, along with Dwarf Berserkers and Halfling Pony Riders, where enchanting T1 mobs was probably a better idea than enchanting heroes. I mean give them Enchanted Weapon and Stone Skin and for all intents and purposes you've got a stack of mini-Warlords.