Nope, the S is 16GB on the base models. It uses either the same Z1 Extreme chip as the non-S or the Z2 Go which is only 4c/8t, and is only 16GB with the latter. I think the former, which just released, has 512/16GB and 1TB/32GB variants.
As for memory sizes, it really depends on the chip. I think the Z1E would likely breathe a bit easier with 24GB but I think 32GB is kind of overkill for it. 16GB is likely plenty for the Z2 Go, and 24GB on the Z2 A in the ROG Xbox Ally is definitely overkill as that's just AMD finally releasing a SKU for the Steam Deck APU, which is two to three generations older than every other Z2 chip.
The Z2, Z2 Go and Z1E all have only 12 graphics cores and that's why I feel like 32GB is overkill for them, whereas the Z2 Extreme has 16 so it actually makes sense to dedicate more than 8GB of memory to it.
I think you've got to remember that "more memory better" doesn't always hold true on a device like a handheld as it does include a cost on battery life even at idle.