I'm going to go image by image and (try to) debunk what people assume to be Sukuna having inherently different shikigami than Megumi. I have no agenda other than trying to truly depict Sukuna's skill, and how having the same shikigami as Megumi makes his jujutsu skill even more impressive.

This is a test run post in this sub, I might just post the tl;dr bit, i'm not sure. Scroll to the bottom if you don't want to read (I don't blame you).

'Nue': Images 1-5

This is a nue + orochi totality, and we have two pieces of evidence here. Firstly, the 'Nue' is clearly sporting a massive snake as a tail, one clearly resembling orochi. Secondly, the symbol on the forehead of the 'Nue' is orochi's symbol, as seen in image three. Clearly Gege's intend was to depict the nue sukuna summons as a combination with orochi in some sense, otherwise he wouldn't include these details.

"Why did sukuna only use nue handsign if it was a totality" Sukuna does the exact same thing when he summons Agito, only using the Nue handsign.

"Divine Dogs: Totality 'variant'": Images 6-10

I believe that this is not Sukuna's version of normal divine dog: totality (dd:t), but rather the unstable variant of the dd:t. This is supported by two main points, the timing of yorozu's mention of unstable shikigami forms, and the list of stable summons.

To describe the chronological process of how Sukuna uses the unstable dd, we first see him summon dd with both hand signs, this is the split two dogs in unstable form, then, upon yorozu's destruction of one of the unstable dogs by liquid metal (image 7), we see the dd:t 'variant' suddenly appear, despite no re-summoning handsigns.

Now in image 8, we see yorozu destroying the unstable dd:t, as it is no longer present in any more panels, UNTIL image 9, where Sukuna uses a specific handsign to resummon only one of the SPLIT unstable dogs. What is this handsign? It is exactly half of the full dd handsigns, which is synonymous with only one unstable dog appearing. (this is just an irrelevant point I wanted to mention)

Then in image 10, after sukuna has summoned stable forms of round deer and piercing ox, we hear yorozu analyse exactly what unstable forms were. Specifically, she says sukuna "prevented complete destruction" by keeping them as unstable. Which is obviously signifying/justifying the fact that sukuna was able to resummon the divine dogs (image 9) again, even after the dd:t 'variant' was destroyed, which means the dd:t variant is simply just the unstable version of the dd:t, not sukuna's specific variant.

This is further backed up by the fact that Yorozu specifically mentions round deer and piercing ox being stable summons in contrast, but never mentions dd:t alongside them, which only further proves that the dd:t variant we saw was not a result of sukuna having inherently different ten shadows, but rather that they are the unstable variant.

tl;dr : the totality we see is actually just an unstable variant, shown as it is destroyed yet resummoned, and yorozu specifically does not mention it as a stable form.

'Addressing Normal Rabbits': Images 11-12

This isn't a debunk of any sort, but really just evidence against the idea that Sukuna's shikigami have inherently different variants. The bunnies we see in both images 11 and 12 are visually no different from megumi's rabbit swarm.

It's not outright evidence against, but does establish that there is evidence of the contrary, and shows that we can make the assumption they are the same, especially as they are depicted similar in two different arcs.

'Max Elephant Variant': Images 13-15

This is the only 'variant' I'm genuinely not sure of, but I do still believe that gege intends to depict this 'variant' as a unstable form, in both narrative and appearance.

Firstly, this is the first and only time where Gege introduces the idea of unstable shikigami. He specifically mentions both piercing ox and tranquil deer to be stable forms, and previously has only shown one single case of unstable forms. It would follow that gege would aim to depict another angle/example of unstable variants, as he introduces it as a concept global to all shikigami.

This is further backed up by the advantages of unstable shikigami, appearance of the shikigami and chronological progression of the fight. Firstly, the most obvious case where he would need to utilise (and narratively depict) the one other benefit of unstable shikigami, their increased effective range.

Since Sukuna aims to use extreme height, as depicted by the wide panel in image thirteen, to increase the crushing force of max elephant, he would clearly need an unstable shikigami to HOLD FORM ACROSS AN EXPANDED RANGE. This is gege intending to depict the second advantage of unstable form, why else would he mention it?

Further supported by the depiction of rabbits being completely equal in appearance to megumi's in the scene just before, creating contrast to elephants more shadow-y appearance, completely blank with void eyes despite being the most colourful and detailed shikigami we've seen, to more clearly demonstrate that this max elephant is an unstable form).

TL;DR - Read this if you want something short

Divine Dogs & Max Elephant - Two Unstable Variants

Gege uses divine dogs and max elephant narratively to depict the two explicitly labelled advantages of unstable form shikigami; preventing complete destruction & expanded effective range.

Divine Dogs are clearly stated to be unstable variants, INCLUDING THE TOTALITY. This is proven since we see the both the totality and non-totality being destroyed, yet even still, sukuna is able to summon non-totality unstable divine dog after. If the totality was not unstable, then they could not be resummoned, and yorozu would include them within her list of stable shikigami.

Max Elephant is gege's less clear unstable variant, used to depict the expanded range advantage of unstable summons. This narratively follows because gege never depicted long range use of the shikigami in the fight except for the one time he uses max elephant, from an extreme height to use acceleration to gain crushing force, which could only be possible with increased distance/range from an unstable summon.

Max Elephant is further supported as it is depicted alongside rabbits, however while the rabbits are completely identical in appearance (across two arcs too) to Megumi's, the max elephant is the opposite, it is the complete opposite of megumi's max elephant, which is the most detailed and colourful shikigami, this one has void eyes and almost-blank body. Gege specifically uses this contrast in similarities to depict max elephant as an unstable summon, such that he can use it to demonstrate the second advantage of unstable summons.

Nue + Orochi Fusion

The Nue we see sukuna summon is simply a nue + orochi mix. It clearly sports orochi's symbol on its head and it's tail is orochi itself. He only uses the nue handsign to summon agito, and likewise for the nue + orochi mix.

Mahoraga Statement

In the volume extras of one of the modulo volumes, gege mentions that all of the versions we see of mahoraga are the exact same in strength. They are also the exact same in appearance. While this isn't outright proof that Sukuna doesn't have outright variants, pair this with the fact that rabbits aren't any different, and that we haven't seen a single other time of a variant, it only supports my point further.

End
If you think you have something to prove me wrong please mention it, but please read the fatter version of what I write above, it goes into more depth and may already answer your question. Also please be nice I'm just a little guy..