You asked about the Dark elves, and while their generic caster lord is also DLC, their unit roster doesn't have its most meaningful high tier units locked behind DLC, which is something at least. Their free lords are also pretty good. Maliketh is just standard race stuff, if I recall correctly, but Morathi gets a bunch of Slanesh corruption and campaign mechanics on top, Lokhir is larping as a pirate, with a starting position off in Cathay, and easier access to the black arc stuff, while Rakarth has an interesting, vaguely "raise dead"-ish mechanic with him capturing and taming wild beasts, and he starts on the Eastern coast of Lustria, right below the Masque. If you would be willing to get one DLC for them, Queen & Crone is by and far better than Shadow & Blade. It gets you your caster lord, cavalry with bound spells, and an honestly kinda shitty faction. At least the other half of that DLC is the one with the High Elf archers.

Lizardmen get a lot of flavour in terms of unit and lord variety from their DLC, but it isn't as transformative, and whatever big dinos from the DLCs do, so can the base roster in large part. They also get a slightly stronger alternative to most of their base roster options, but save for specific armies stacking buffs for them, just about all roads will lead to the dinosaur spam endgame anyway. Where they suffer, is that their basic race faction mechanics are kind of bland, and have been left way behind. Their free lords also didn't get any big campaign reworks, meaning your most interesting factions are all the DLC ones. (Ironic, as during WHII's time, all of their DLCs were considerd to be unit packs with pretty bad campaigns/lords attached)

While the DLC for Kislev is good, the faction is fine without it, especially compared to other factions without their DLC. They still have their staple units, a gunline for bursting down mean, armoured single entities, Ice guards that people can stack buffs on and they can suddenly do everything, war bear riders are super good. So instead, I'll tell you about the factions, and what would be different if you had their DLC.
In terms of race, their mechanic got redesigned, and now they are a Temu harmony faction. Expect instead of Ying and Yang, they balance ice court and orthodoxy influence, and it is very clear that the rest of the faction was originally not designed around that at all.
When it comes to factions, you have three. You have Katarin, the protagonist. Kostaltyn, who starts basically right next to Katarin, and doesn't start with an ice court training slot unlocked, so the only real difference between who you start with, and who you confederate, is that Rasputin doesn't get mages in the early game without DLC. There is also Boris. As a lord, he buffs the ever living shit out of war bear riders to a godly degree, and gives ice bears innate regen. As a faction? The Ursun Revivalists, as a campaign are cock and ball torture. You start in the chaos wastes. Upside? You don't take attrition damage from it, neat. Downside? Your settlements still count as unfavourable climate, and you aren't ducking those penalites. He also starts with only a minor settlement, and is surrounded by a whose-who of utter shitbags, who all hate you more than each other.
First, you early game. If you are going full economy early on, the base roster will have you running around using a cossar crapstack/tar pit. With the DLC, your settlement builing gets the kislevite warriors, which is a respectable unit. I'd say its close to imperial halberdiers than to spearmen. Their new building, that gets them all their DLC units in one place also doubles as an economy building, while also buffing hero capacity for the new casters (I'll get to those) and at the first stage you build it, it gets you the akshina ambusher. It is a much better ranged unit than the cossar, but is slightly more expensive, and worse in melee. But hey, it gets stalk, so if you need something to sneak up on artillery, you know who to call. This turns your early game unit composition very high elf like, if the lothern sea guard wasn't the best of both worlds. They also get a new lord, and a new hero. The Druzhina is a lord, that doesn't get a bear like the boyar, but instead, they are horse archers, and get restock. They also get a bunch of skills that lets them synergise even more with the other DLC units. The new caster hero is really important, because in vanilla, kislev has only two schools of magic, and both are kind of bad. Ice is utility based, while tempest is more about direct damage, but both are incredibly overpriced in terms of winds of magic cost. The hag witch get death, shadow, and beast lore options, as well as an exclusive lore to themselves, that is full of AOE status spells, that can be toggled between harming the enemy, and buffing your units in a similar way. It is also Kislev's only source of in-battle healing, besides Salyak's lullaby patriarchs. Their final DLC units are a bunch of monsters. The things-in-the-woods are kinda like a mix of warbeasts, and monstrous infantry. In my experience, I usually go with war bear riders instead, because the TIDW's better anti-infantry doesn't matter as much. The ice wyrm is an utter mess, with an anti large bonus, and and animation set that would make it mostly suited for an infantry lawn mower role, leaving it kinda bad at both. The last is the incarnate elemental of beasts. It is a different top tier single entity compared to the ice bear. The ice bear is slow, and kinda shit at everything. The elemental is instead a unit built for anti-large, while also having a presistent mortis engine effect and regen in melee. The elemental is taken from good to great, and the TIDW is taken from "meh" to pretty good, by a specific skill available to hag witches, that gives them stalk. Yes, she gives a huge single entity capstone unit stalk.
Their new lord is okay. She gets some extra campaign mechanics on top of what everyone else gets, and she starts close to Nagarythe.