Total War: Warhammer

If you mean like tech tree upgrades that gives all your infantry +3dmg or your cav +5%movespeed, this doesn't have a visual representation. If you mean different weapon types/armor types, then that's 2 different units in the game, for example normal infantry with sword+shield and infantry with halberds are just different units, you can't give halberds to existing units, you need to recruit halberdiers(and disband your swordsmen if you don't want them anymore). Those have visual differences since they're not the same unit. If you mean lord item upgrades, those also have visual differences in some cases. When you find the flaming sword of coolbadassness, your hero will have a flaming sword in combat. Those are very limited though, there's basically only a specific set of item for your legendary lord based on the warhammer lore. There's also random magic items that aren't tied to a specific hero in the warhammer lore but those aren't physically represented.

Units have a decent amount of visual variations within the same unit type too, not like huge, but they have slightly different shields or weapon, so it's not like the clone wars. They might also add army colors at some point, although it's unclear. There's currently armor colors for enemy armies and shit, but you can't seem to select yours sadly, which sucks. Maybe mods will help there.

But yeah in terms of any physcal upgrades to the units, it's just different unit types. You can't customize those. Like taking Vampire Counts as an example, you can only do 2 black knights types, either normal black knights with swords, or black knights with both barding and lances. Can't put barding on normal black knights, can't have just lances, it's a package. Only exception is the mount of your lord, which is customized separately, so you can have a normal mount, a mount with barding/improved performance, a flying mount and a monstruous mount(that's the general pattern, not every lord can have the last 2 types though).

Game's definitely not feature complete if you compare to Warhammer tabletop or even past Total Wars, but that's the cost of having so many widely different unit models I guess. It's possible that whenever they add the unit+lord DLCs to existing races, they'll also add more variations to existing units at the same time. Or they'll be moddable.

Oh yeah I hadn't checked the empire tech tree, those kinda sounds like they could be visual upgrades but they aren't, just small number tweaks. At least I haven't noticed it, I haven't played the game yet but it seemed like people further in the campaign still had the same looking units than early on.

That said as I pointed out, with all the customization things, it's stuff that could potentially be added as mods, if people bother making them. They could make small unit variations and tie them to upgrades and what not I'd assume. Game has mod support, or will have it(they said it'll be in, but they've been silent about confirming wether or not it'd be ready for launch, so I'd expect it later instead, say in a few weeks/a month), so eventually a lot of customization should be available for a lot of stuff, missing units and shit.

Considering this is the only real example of bad AI that seems to have popped up even though various people are uploading hours of campaign with the various races, it would seem it's not that common. I did see some weird AI choices when LegendofTotalWar was cheesing the army by going back and forth with Mannfred only to pick off units with spells, where their entire army kinda just stand there, but it made sense in some cases because they don't have vision of his army(he runs them away/behind trees), or they're standing around their artillery in a defensive position on high ground.

I've watched a lot of the game, and it doesn't seem it has too many issues. One major issue I've noted is in one of the campaigns, one guy who's apparently playing a bunch of races in parallel seems to have lost a large amount of his skill points on his hero. Not sure if save corruption or what. Problem is he didn't upload all his playthrough, it jumps from turn 28 or so in which he's not bugged to like turn 40 where he's bugged in the next video, so it's hard to tell what happened in the middle, at which point it happened and shit like that. You definitely want to make saves every few turns I would think, just in case of, since losing 5skill points(I think that's what he lost) would be a major issue for progressing the campaign. Another is that balance seems poor in some specific spots. Like overall there might be balance issues, but a few specific things are vastly OP and abusing them would trivialize the campaign(and multiplayer to an extent). It's mostly spells/abilities being way OP.